First measurement of the {\mathbf{|\textit t|}}-dependence of coherent \mathbf{\rm{J/ψ}} photonuclear production
aa r X i v : . [ nu c l - e x ] J a n EUROPEAN ORGANIZATION FOR NUCLEAR RESEARCH
CERN-EP-2021-0035 January 2021© 2021 CERN for the benefit of the ALICE Collaboration.Reproduction of this article or parts of it is allowed as specified in the CC-BY-4.0 license.
First measurement of the | t | -dependence of coherent J / ψ photonuclearproduction ALICE Collaboration * Abstract
The first measurement of the dependence on | t | , the square of the momentum transferred between theincoming and outgoing target nucleus, of coherent J / ψ photoproduction is presented. The data weremeasured with the ALICE detector in ultra-peripheral Pb–Pb collisions at a centre-of-mass energyper nucleon pair √ s NN = .
02 TeV with the J / ψ produced in the central rapidity region | y | < . x range ( . − . ) × − .The measured | t | -dependence is not described by computations based only on the Pb nuclear formfactor, while the photonuclear cross section is better reproduced by models including shadowing ac-cording to the leading-twist approximation, or gluon-saturation effects from the impact-parameter de-pendent Balitsky–Kovchegov equation. This new observable is therefore a valid tool to constrain therelevant model parameters and to investigate the transverse gluonic structure at very low Bjorken- x . * See Appendix A for the list of collaboration members irst measurement of the | t | -dependence of coherent J / ψ photonuclear productionALICE Collaboration Photonuclear reactions can be studied in ultra-peripheral collisions (UPCs) of heavy ions where thetwo projectiles pass each other with an impact parameter larger than the sum of their radii. In this case,purely hadronic interactions are suppressed and electromagnetically induced processes occur via photonswith typically very small virtualities, of the order of tens of MeV . The intensity of the photon flux isproportional to the square of the electric charge of the nuclei, resulting in large cross sections for thecoherent photoproduction of a vector meson in UPCs of Pb ions at the LHC. This process has a clearexperimental signature: the decay products of the vector meson are the only particles detected in anotherwise empty detector.The physics of vector meson photoproduction is described, e.g., in Refs. [1–4]. Two vector mesonphotoproduction processes, coherent and incoherent, are relevant for the results presented here. In theformer, the photon interacts with all nucleons in a nucleus, while in the latter it interacts with a singlenucleon. In both cases a single vector meson is produced. Experimentally, one can distinguish be-tween these two production types through the transverse momentum p T of the vector meson which isrelated to the transverse size of the target. While coherent photoproduction is characterised by an aver-age transverse momentum h p T i ∼
60 MeV/ c , incoherent production leads to higher average transversemomenta: h p T i ∼
500 MeV/ c . Incoherent photoproduction can also be accompanied by the excitationand dissociation of the target nucleon resulting in an even higher transverse momentum of the producedvector meson [5].Shadowing, the observation that the structure of a nucleon inside nuclear matter is different from that ofa free nucleon [6], is not yet completely understood and several processes may have a role in differentkinematic regions. In this context, coherent heavy vector meson photoproduction is of particular inter-est, because it is especially sensitive to the gluon distribution in the target, and thus to gluon shadowingeffects at low Bjorken- x [7, 8]. One of the effects expected to contribute to shadowing in this kinematicregion is saturation, a dynamic equilibrium between gluon radiation and recombination [9]. The mo-mentum scale of the interaction ( Q ) is related to the mass m V of the vector meson as Q ∼ m V / x of the gluonicexchange as x = (cid:0) m V / √ s NN (cid:1) exp ( ± y ) , where the two signs indicate that either of the incoming ionscan be the source of the photon. Thus, the charmonium photoproduction cross section at midrapidity inPb–Pb UPCs at the LHC Run 2 centre-of-mass energy per nucleon pair of √ s NN = .
02 TeV is sensitiveto x ∈ ( . , . ) × − . It thereby provides information on the gluon distribution in nuclei in a kinematicregion where shadowing could be present and saturation effects may be important [10, 11].Charmonium photoproduction in ultra-peripheral Pb–Pb collisions was previously studied by the ALICECollaboration at √ s NN = .
76 TeV [12–14]. The coherent J / ψ photoproduction cross section was mea-sured both at midrapidity | y | < . − . < y < − .
6. Recently, a measurementof the rapidity dependence of coherent J / ψ photoproduction at forward rapidity at the higher energy of √ s NN = .
02 TeV was also published by the ALICE Collaboration [15]. In addition, the CMS Col-laboration studied the coherent J / ψ photoproduction accompanied by neutron emission at semi-forwardrapidity 1 . < | y | < . √ s NN = .
76 TeV [16]. These measurements allow for a deeper insightinto the rapidity dependence of gluon shadowing, but do not give information on the behaviour of glu-ons in the impact-parameter plane. The square of the momentum transferred to the target nucleus, | t | ,is related through a two-dimensional Fourier transform to the gluon distribution in the plane transverseto the interaction [17]; thus the study of the | t | -dependence of coherent J / ψ photoproduction providesinformation about the spatial distribution of gluons as a function of the impact parameter. Thus far, theonly measurement in this direction was performed recently by the STAR Collaboration for the case ofthe ρ vector meson [18]; that is, for a process with a semi-hard scale.2irst measurement of the | t | -dependence of coherent J / ψ photonuclear productionALICE CollaborationIn this Letter, the first measurement of the | t | -dependence of the coherent J / ψ photoproduction crosssection at midrapidity in Pb–Pb UPCs at √ s NN = .
02 TeV is presented. The J / ψ vector mesons werereconstructed in the rapidity range | y | < . µ + µ − , taking advantage of thebetter mass and momentum resolution of this channel with respect to the e + e − channel. The data sample,recorded in 2018, is approximately 10 times larger than that used in previous ALICE measurements atmidrapidity at the lower energy of √ s NN = .
76 TeV [14]. Cross sections are reported for six | t | intervalsand compared with theoretical predictions. The ALICE detector and its performance are described in Refs. [19, 20]. Three central barrel detectors,the Inner Tracking System (ITS), the Time Projection Chamber (TPC), and the Time-of-Flight (TOF), inaddition to two forward detectors, V0 and the ALICE Diffractive (AD) arrays, are used in this analysis.The central barrel detectors are surrounded by a large solenoid magnet producing a magnetic field of B = . . < η < . − . < η < − .
7, respectively. Both counters are segmented in four rings in the radial direction, with each ringdivided into 8 sections in azimuth.The AD consists of two scintillator stations, ADA and ADC, located at 16 and −
19 m along the beamline with respect to the nominal interaction point and covering the pseudorapidity ranges 4 . < η < . − . < η < − .
9, respectively [21, 22].The ITS is a silicon based detector and is made of six cylindrical layers using three different technologies.The Silicon Pixel Detector (SPD) forms the two innermost layers of the ITS and covers | η | < | η | < .
4, respectively. Apart from tracking, the SPD is also used for triggering purposes and to reconstructthe primary vertex.The ITS is cylindrically surrounded by the TPC, whose main purpose is to track particles and providecharged-particle momentum measurements with good two-track separation and particle identification.The TPC coverage in pseudorapidity is | η | < . c to 100 GeV/ c .The TOF is a large cylindrical gaseous detector based on multi-gap resistive-plate chambers. It coversthe pseudorapidity region | η | < .
8. The TOF readout channels are arranged into 18 azimuthal sectorswhich can provide topological trigger decisions.
The online event selection was based on a dedicated UPC trigger which selected back-to-back tracksin an otherwise empty detector. This selection required ( i ) that nothing above the trigger threshold wasdetected in the V0 and AD detectors, ( ii ) a topological trigger requiring less than eight SPD chips withtrigger signal, forming at least two pairs; each pair was required to have an SPD chip fired in each of thetwo layers and to be in compatible azimuthal sectors, with an opening angle in azimuth between the twopairs larger than 144 o , ( iii ) a topological trigger in the TOF requiring more than one and less than sevenTOF sectors to register a signal; at least two of these sectors should have an opening angle in azimuthlarger than 150 o . 3irst measurement of the | t | -dependence of coherent J / ψ photonuclear productionALICE CollaborationThe integrated luminosity of the analysed sample is 233 µ b − . The determination of the luminosity isobtained from the counts of a reference trigger based on multiplicity selection in the V0 detector, withthe corresponding cross section estimated from a van der Meer scan; this procedure has an uncertainty of2.2% [23]. The determination of the live-time of the UPC trigger has an additional uncertainty of 1.5%.The total relative systematic uncertainty of the integrated luminosity is thus 2.7%.Additional offline V0 and AD veto decisions were applied in the analysis. The offline veto algorithmimproved the signal to background ratio, because it utilised a larger timing window to integrate the signalthan its online counterpart. Some good events were lost due to this selection. The loss was taken intoaccount with the correction on veto trigger inefficiency discussed in Sec. 3.4. The systematic uncertaintyfrom the V0 and AD vetoes was estimated as the relative change in the measured J / ψ cross sectionbefore and after imposing them and correcting for the losses; it amounts to 3%.Each event had a reconstructed primary vertex within 15 cm from the nominal interaction point along thebeam direction, z , and had exactly two tracks. These tracks were reconstructed using combined trackingin the ITS and TPC. Tracks were requested to have at least 70 (out of 159) TPC space points and to havea hit in each of the two layers of the SPD. Each track had to have a distance of closest approach to theevent interaction vertex of less than 2 cm in the z -axis direction. Also, each track was required to have | η | < .
9. The relative systematic uncertainty from tracking, which takes into account the track qualityselection and the track propagation from the TPC to the ITS, was estimated from a comparison of dataand Monte Carlo simulation. The combined uncertainty to reconstruct both tracks is 2.8%.The particle identification (PID) was provided by the specific ionisation losses in the TPC, which offera large separation power between muons and electrons from the leptonic decays of the J / ψ in the mo-mentum range ( . , . ) GeV/ c , relevant for this analysis. The effect of a possible misidentification wasfound to be negligible.An offline SPD decision was also applied in the analysis. The offline topological SPD algorithm ensuredthat the selected tracks crossed the SPD chips used in the trigger decision. The relative systematicuncertainty from the SPD and TOF trigger amounts to 1.3%, which was estimated using a data-drivenmethod by changing the requirements on the probe tracks.The selected events were required to have tracks with opposite electric charge, the rapidity of the dimuoncandidate was restricted to | y | < . p T had to be less than 0.11 GeV/ c , in order to obtain asample dominated by coherent interactions with just a small contamination from incoherent processes.The measurement was initially carried out in p intervals, because for collider kinematics | t | ≈ p . Thecorrections needed to obtain the | t | -dependence are discussed in Sec. 3.7. As a first step in extracting the coherent J / ψ signal, a fit to the opposite sign dimuon invariant massdistribution was performed. The model used to fit the data consists of three templates: one Crystal Ballfunction [24] (CB) to describe the J / ψ resonance, a second CB function to describe the ψ ′ resonance,and an exponential function to describe the continuum production of muon pairs, γγ → µ + µ − .The parameters of the exponential function were left free. The integral of this exponential in the massrange ( . , . ) GeV/ c was used to determine the number of events from the continuum production inthis interval.The CB parameters describing the tails of the measured distribution in data, commonly known as α and n , were fixed to the values obtained while fitting the dimuon invariant mass distribution in an associatedMonte Carlo simulation, which is described in Sec. 3.4. These settings were employed for both CBfunctions.The number of J / ψ candidates in each p interval was obtained from an extended maximum likelihood4irst measurement of the | t | -dependence of coherent J / ψ photonuclear productionALICE Collaborationfit to the unbinned invariant mass distribution of all µ + µ − pairs which survived the selection criteriadescribed in Sec. 3.1. Results of the fits for the six p intervals are shown in Fig. 1. In all cases a veryclear J / ψ resonance is seen over a fairly small background.The relative systematic uncertainty from the signal extraction was calculated by repeating the fit over dif-ferent invariant mass ranges, and modifying the CB α and n parameters accordingly. These uncertaintiesvary in the interval (0.7,2.2)%. The selection criteria described above are not sensitive to events which mimic the signature of coherentJ / ψ production, but are coming from feed-down of ψ ′ or incoherent production. The contribution ofthese events was taken into account with the f D and f I factors, respectively, entering Eq. (1), N cohJ / ψ = N fit + f I + f D × ( Acc × ε ) cohJ / ψ , (1)where N fit , the yield of J / ψ candidates, is the integral of the CB describing the J / ψ signal in the fit ofthe dimuon invariant mass spectrum, and ( Acc × ε ) cohJ / ψ is the acceptance and efficiency correction factordescribed in Sec. 3.4.Feed-down refers to the decay of a ψ ′ to a J / ψ plus anything else, where these additional particles werenot detected for some reason. The correction for these events, f D , was estimated with Monte Carlosimulations describing the apparatus (Acc × ε ) factor for the following channels: J / ψ → µ + µ − , ψ ′ → µ + µ − , and ψ ′ → J / ψ + X; and the measured ratio of ψ ′ to J / ψ production cross sections. The detailsof the method are described in Ref. [15]. The results for each p interval are summarised in Table 1.Relative systematic uncertainties, estimated by using different cross section ratios, are p -correlated.Their relative effect on the final cross section can be found in Table 2; it is well below 1%.Most of the incoherent production of J / ψ off nucleons was rejected with the restriction of the phase spacein p T , as mentioned in Sec. 3.1. However, around 5% of all incoherent events remained in the regionwhere the measurement was performed. To estimate the f I factor to correct for the remaining incoherentevents, a fit to the measured J / ψ p T distribution of data in the invariant mass range ( . , . ) GeV/ c was used. The model fitted to the data consists of six templates: coherent J / ψ photoproduction, in-coherent J / ψ photoproduction, incoherent J / ψ photoproduction with nucleon dissociation, coherent ψ ′ photoproduction, incoherent ψ ′ photoproduction, and continuum production from γγ → µ + µ − . Thetemplates of all, but dissociative J / ψ and continuum, were taken from Monte Carlo simulations. In thefit, the fractions of both ψ ′ photoproduction processes were fixed to values calculated as described above.These included the modifications that the p T restriction was released and that there was a selection on theinvariant mass to be in the range ( . , . ) GeV/ c . Other fractions were left free in the fit. The normal-isation of the continuum was restricted from the invariant mass fit to be the sum of background eventsin the mass range of the J / ψ . The shape of the continuum was taken from the dimuon p T distributionselecting the invariant mass range between the J / ψ and the ψ ′ , while the shape for the nucleon dissoci-ation process was based on the H1 parameterisation [25]. The global template was fitted to data usingan extended maximum likelihood unbinned fit. The results for each p interval are reported in Table 1.The systematic uncertainties, estimated from a combination of the fit uncertainty and a modification ofthe coherent template used in the fitting model are p T -correlated. Their relative effect on the final crosssection can be found in Table 2. The STARlight 2.2.0 MC generator [26] was used to generate samples of coherent and incoherent eventsfor the production of J / ψ → µ + µ − and ψ ′ → µ + µ − + π + π − ( π π ) . GEANT 3.21 [27] was used to5irst measurement of the | t | -dependence of coherent J / ψ photonuclear productionALICE Collaboration ) c (GeV/ µµ m ) c C oun t s pe r ( M e V / = 5.02 TeV NN s Pb − ALICE, Pb - µ + µ → ψ J/ -1 b µ ± = 233 int UPC, L c GeV(0.0000,0.0007) ∈ T2 p | < 0.8 y | -31+28 = 569 ψ J/ N ) c (GeV/ µµ m ) c C oun t s pe r ( M e V / = 5.02 TeV NN s Pb − ALICE, Pb - µ + µ → ψ J/ -1 b µ ± = 233 int UPC, L c GeV(0.0007,0.0016) ∈ T2 p | < 0.8 y | -25+26 = 551 ψ J/ N ) c (GeV/ µµ m ) c C oun t s pe r ( M e V / = 5.02 TeV NN s Pb − ALICE, Pb - µ + µ → ψ J/ -1 b µ ± = 233 int UPC, L c GeV(0.0016,0.0026) ∈ T2 p | < 0.8 y | -24+24 = 511 ψ J/ N ) c (GeV/ µµ m ) c C oun t s pe r ( M e V / = 5.02 TeV NN s Pb − ALICE, Pb - µ + µ → ψ J/ -1 b µ ± = 233 int UPC, L c GeV(0.0026,0.0040) ∈ T2 p | < 0.8 y | -22+23 = 469 ψ J/ N ) c (GeV/ µµ m ) c C oun t s pe r ( M e V / = 5.02 TeV NN s Pb − ALICE, Pb - µ + µ → ψ J/ -1 b µ ± = 233 int UPC, L c GeV(0.0040,0.0062) ∈ T2 p | < 0.8 y | -20+21 = 388 ψ J/ N ) c (GeV/ µµ m ) c C oun t s pe r ( M e V / = 5.02 TeV NN s Pb − ALICE, Pb - µ + µ → ψ J/ -1 b µ ± = 233 int UPC, L c GeV(0.0062,0.0121) ∈ T2 p | < 0.8 y | -51+21 = 401 ψ J/ N Figure 1:
Invariant-mass distributions for different p intervals with the global fit described in the text shown withthe blue line. The exponential part of the fit model, representing the γγ → µ + µ − background, is shown in red. | t | -dependence of coherent J / ψ photonuclear productionALICE Collaboration Table 1:
Incoherent correction f I , feed-down correction f D and the ( Acc × ε ) cohJ / ψ correction factor for each p interval. See Eq. (1). p interval (GeV / c ) f I f D ( Acc × ε ) cohJ / ψ ( , . ) ( . , . ) ( . , . ) ( . , . ) ( . , . ) ( . , . ) ( Acc × ε ) cohJ / ψ , are shown in Table 1 for the different p intervals used in this analysis.AD and V0 were used to veto activity at forward rapidity. These detectors were sensitive to signalscoming from independent interactions (pile-up), which resulted in the rejection of potentially interestingevents. The correction factor for this effect was obtained using a control sample of events collected withan unbiased trigger. These were then used to compute the probability of having a veto from AD or V0in otherwise empty events. The total veto trigger efficiency ε VETO used in Eq. (2) was determined to be0.94. The corresponding systematic uncertainty is included in the AD and V0 value of 3% mentioned inSec. 3.1.Electromagnetic dissociation (EMD) is another process which may cause the rejection of a good eventdue to the veto from the forward detectors. EMD can occur when photons excite one or both interactingnuclei. Upon de-excitation, neutrons and sometimes other charged particles are emitted at forward ra-pidities [28] and can trigger a V0 or AD veto. Such loss of events was quantified from data gathered witha specialized EMD trigger; the efficiency correction factor to take into account these losses amounts to ε EMD = .
92 with a relative systematic uncertainty of 2% given by the statistical uncertainty from thecontrol sample. p T distribution Cross sections were measured in different p intervals. In order to account for the migration of about45% of the events across p intervals due to the finite resolution of the detector, an unfolding procedurewas used.Amongst many available methods, unfolding based on Bayes’ theorem [29] was chosen to perform theunfolding, while the singular-value decomposition (SVD) method [30] served to study potential system-atic effects. The implementations of these methods as provided by RooUnfold [31] were used in thisanalysis.Bayesian unfolding is an iterative method, therefore the result depends on the number of iterations.The size of the data sample is large enough to investigate different numbers of p ranges. These twoparameters, that is the number of iterations and of ranges, were tuned using Monte Carlo simulationsby studying the evolution of the statistical uncertainty in each interval as a function of the number ofiterations, and by using the relative difference between iteration-adjacent results. It was found that thebest combination for this analysis is Bayes’ unfolding with three iterations applied to the p distributionsplit into six regions. The widths of the p intervals were chosen to have similar statistical uncertaintiesin each region.The Monte Carlo sample used for unfolding contained 600 000 events. An 80% fraction of them was usedto train the response matrix which is used to unfold the true distribution from the measured distribution.7irst measurement of the | t | -dependence of coherent J / ψ photonuclear productionALICE CollaborationThis matrix was tested on the remaining 20% of the events. The unfolding matrix was able to correctthe smeared distribution with high precision. Comparison with results using the SVD method revealed a p T -correlated relative systematic uncertainty with values in the interval (0.6,2.3)%. J / ψ photoproduction in UPCs The differential cross section for coherent J / ψ photoproduction in a given p interval and a given rapidityrange ∆ y in Pb–Pb UPCs isd σ cohJ / ψ d y d p = unf N cohJ / ψ ε VETO × ε EMD × BR ( J / ψ → µ + µ − ) × L int × ∆ p × ∆ y , (2)where the correction factors ε VETO and ε EMD are introduced in Sec. 3.4, BR ( J / ψ → µ + µ − ) is the branch-ing ratio (5 . ± . L int is the total integrated luminosity of the data sample, ∆ p t is the sizeof the interval where the measurement was performed, and finally, unf N cohJ / ψ is the number of coherent J / ψ candidates after unfolding the results given by Eq. (1). The corresponding systematic uncertainties aresummarised in the upper part of Table 2. With the exception of signal extraction, all other systematicuncertainties mentioned up to here are correlated across p intervals. The cross section described by Eq. (2) is the one measured by ALICE. The main theoretical interest is inthe photonuclear process at a fixed energy. To obtain the corresponding cross section, one has to accountfor several effects. None of these effects is affected by the ALICE detector, they just depend on thekinematics and quantum nature of the process. This means that the uncertainties in going from the UPCto the photonuclear cross sections are of theoretical nature only.At midrapidity, the UPC cross section corresponds to the γ Pb cross section multiplied by twice the photonflux, n γ Pb ( y ) , d σ cohJ / ψ d y d p (cid:12)(cid:12)(cid:12)(cid:12)(cid:12) y = = n γ Pb ( y = ) d σ γ Pb d | t | . (3)Since the rapidity dependence of the UPC cross section in the rapidity range studied here is fairly flat, themeasurements are taken to represent the value at y =
0. In UPCs, there are two potential photon sources,so in principle both amplitudes have to be added and their interference needs to be accounted. This wasstudied for the first time in Ref. [33] and later measured for the case of ρ coherent photoproduction bythe STAR Collaboration [34]. The interference is important only at very small values of | t | . To accountfor this effect, the STARlight program, which includes the interference of both amplitudes, was used. Itwas found that this is an 11.6% effect in the smallest | t | interval, where the effect is concentrated. Toestimate the potential uncertainty on this procedure, the interference effects with the nominal strengthwere compared to those with a 25% reduction of the strength. The relative change in the photonuclearcross section varied from 0.3 to 1.2% with the largest uncertainty being assigned to the smallest | t | interval.The photon flux was computed in the semiclassical formalism following the prescription detailed inRef. [35] and cross checked with that of Ref. [36]. The flux amounts to 84.9 with an uncertainty of 2%coming from variations of the geometry of the Pb ions.Although the value of p is a good approximation to that of | t | , it is not exact due to the fact thatthe photon also has a transverse momentum in the laboratory frame. To account for this effect, thecross section was unfolded with a response matrix built from p - and | t | -distributions. Two sources for8irst measurement of the | t | -dependence of coherent J / ψ photonuclear productionALICE Collaboration Table 2:
Summary of the identified systematic uncertainties on the coherent J / ψ photoproduction and photonu-clear cross sections. The uncertainties to go from the measured cross section in UPCs to the photonuclear processare listed after the line in the middle of the table and their origin depends on the modeling of the photon flux andinterference effects. The correlation across p intervals is discussed in the text. Source Uncertainty (%)Signal extraction (0.7,2.2) f D (0.1,0.5) f I (1.1,2.3) p migration unfolding (0.6,2.3)Luminosity 2.7V0 and AD veto 3EM dissociation 2ITS-TPC tracking 2.8SPD and TOF efficiency 1.3Branching ratio 0.5Variations in interference strength (0.3,1.2)Value of the photon flux at y = p →| t | unfolding (0.1,5.7)the distributions were used: ( i ) the STARlight generator which includes the transverse momenta of thephotons, but does not describe so well the shape of the measured p distribution in data, and ( ii ) measured p values coupled to photon momenta randomly generated using the transverse momentum distributionof photons from Refs. [37, 38]. The average of the corresponding unfolded results was used for the crosssection, while half their difference was taken as a systematic uncertainty which varied between 0.1% and5.7%, with this last value corresponding to the largest | t | interval.These three uncertainties are reported in the lower part of Table 2. The uncertainty on the value of thephoton flux at y = | t | , the uncertainty on the p →| t | unfolding is partially correlatedand the uncertainty on the variation of the interference term is anti-correlated in the lowest | t | region andcorrelated in the other | t | regions. They are added in quadrature for the final result shown in Sec. 4 andTable 3 below. The final result for the cross section measured in each p interval is reported in Table 3. The statis-tical uncertainty originates from the error obtained in the fit to the dimuon invariant-mass distribution,propagating the uncertainties of the f I and f D corrections, see Eq. (1), and the uncertainty related to theunfolding process. The uncorrelated systematic uncertainty from signal extraction and the quadratic sumof correlated systematic uncertainties are shown in Table 3.The results for the photonuclear cross section are listed in Table 3 and shown in Fig. 2, where themeasurement is compared with several theoretical predictions. The average | t | ( h| t |i ) quoted in Table 3was estimated from the | t | -distribution used in the response matrix based on measured data (see above).The mean of the ensuing distribution in a given p interval was taken to be h| t |i .STARlight utilises the vector meson dominance model and a parameterisation of the existing data onexclusive photoproduction of J / ψ off protons coupled with a Glauber-like formalism to obtain the pho-tonuclear cross section. Since the | t | -dependence in this model comes from the nuclear form factor,9irst measurement of the | t | -dependence of coherent J / ψ photonuclear productionALICE Collaboration Table 3:
Measured coherent J / ψ photoproduction cross section in UPCs in different p intervals as well as thephotonuclear cross section in | t | -intervals. The first uncertainty is statistical, the second and third systematic,uncorrelated and correlated, respectively. The fourth uncertainty, for the photonuclear cross section case, is thesystematic uncertainty on the correction to go from the UPC to the photonuclear cross section. The mean value of | t | in each interval is also shown. Interval (GeV c − ) h| t |i (GeV c − ) d σ cohJ / ψ d y d p ( mb c GeV ) d σ γ Pb d | t | ( mb c GeV ) ( , . ) × − ± ± ±
73 8.15 ± . ± . ± . ± . ( . , . ) × − ± ± ±
60 5.75 ± . ± . ± . ± . ( . , . ) × − ± ± ±
43 4.23 ± . ± . ± . ± . ( . , . ) × − ± ± ±
27 2.87 ± . ± . ± . ± . ( . , . ) × − ± ± ±
14 1.48 ± . ± . ± . ± . ( . , . ) × − ± ± ± ± . ± . ± . ± . high shadowing and theother low shadowing . The low shadowing prediction is shown in Fig. 2. The shape obtained from thismodel is similar to that of the data and describes the cross section within experimental uncertainties. Asshown in Fig. 3 of [10], the high-shadowing version of the model has a similar shape but the overallnormalisation is smaller by factor around 1.7.The b-BK model by Bendova et al. [11, 40, 41] is based on the colour dipole approach where the scat-tering amplitude is obtained from the impact-parameter dependent solution of the Balitsky–Kovchegovequation coupled to a nuclear-like intial condition [42, 43] which incorporates saturation effects. Thismodel also predicts the behaviour of the data quite well.The different predictions of the STARlight and LTA or b-BK models reflect the effects of QCD dynamics(shadowing in LTA, saturation in b-BK) at small values of x ∼ − and highlight the importance ofmeasuring the | t | -dependence of the photonuclear cross section. The first measurement of the | t | -dependence of coherent J / ψ photonuclear production off Pb nucleiis presented. The measurement was carried out with the ALICE detector at midrapidity, | y | < .
8, inultra-peripheral Pb–Pb collisions at √ s NN = .
02 TeV and covers the small- x range ( . − . ) × − .Photonuclear cross sections in six different intervals of | t | are reported and compared with theoreticalpredictions. The measured cross section shows a | t | -dependent shape different from a model based onthe Pb nuclear form factor and closer to the shape predicted by models including QCD dynamical effectsin the form of shadowing (LTA) or saturation (b-BK). The difference in shape between the LTA andb-BK models is smaller than the current measurement uncertainties, but the large data sample expectedin the LHC Run 3 [44] and the improvement in tracking from the upgrades of the ALICE detector [45]promise a much improved accuracy. These results highlight the importance of observables sensitive tothe transverse gluonic structure of particles for extending the understanding of the high-energy limit ofQCD. 10irst measurement of the | t | -dependence of coherent J / ψ photonuclear productionALICE Collaboration ) - G e V c | ( m b t / d | P b γ σ d = 5.02 TeV NN s ψ Pb+Pb+J/ → ALICE Pb+Pb STARlight (Pb form factor)LTA (nuclear shadowing)b-BK (gluon saturation) , |y|<0.8 ψ ALICE coherent J/ Experimental uncorrelated syst. + stat. Experimental correlated syst.Pb model uncertainty γ UPC to -2 c | (GeV t |11.52 M ode l / D a t a STARlight / DataLTA / Datab-BK / Data
Figure 2:
Dependence on | t | of the photonuclear cross section for the coherent photoproduction of J / ψ off Pbcompared with model predictions [10, 11, 26] (top panel). Model to data ratio for each prediction in each measuredpoint (bottom panel). The uncertainties are split to those originating from experiment and to those originating fromthe correction to go from the UPC to the photonuclear cross section. Acknowledgements
The ALICE Collaboration would like to thank all its engineers and technicians for their invaluable con-tributions to the construction of the experiment and the CERN accelerator teams for the outstandingperformance of the LHC complex. The ALICE Collaboration gratefully acknowledges the resourcesand support provided by all Grid centres and the Worldwide LHC Computing Grid (WLCG) collab-oration. The ALICE Collaboration acknowledges the following funding agencies for their support inbuilding and running the ALICE detector: A. I. Alikhanyan National Science Laboratory (YerevanPhysics Institute) Foundation (ANSL), State Committee of Science and World Federation of Scientists(WFS), Armenia; Austrian Academy of Sciences, Austrian Science Fund (FWF): [M 2467-N36] andNationalstiftung für Forschung, Technologie und Entwicklung, Austria; Ministry of Communicationsand High Technologies, National Nuclear Research Center, Azerbaijan; Conselho Nacional de Desen-volvimento Científico e Tecnológico (CNPq), Financiadora de Estudos e Projetos (Finep), Fundação deAmparo à Pesquisa do Estado de São Paulo (FAPESP) and Universidade Federal do Rio Grande do11irst measurement of the | t | -dependence of coherent J / ψ photonuclear productionALICE CollaborationSul (UFRGS), Brazil; Ministry of Education of China (MOEC) , Ministry of Science & Technology ofChina (MSTC) and National Natural Science Foundation of China (NSFC), China; Ministry of Scienceand Education and Croatian Science Foundation, Croatia; Centro de Aplicaciones Tecnológicas y De-sarrollo Nuclear (CEADEN), Cubaenergía, Cuba; Ministry of Education, Youth and Sports of the CzechRepublic and Czech Science Foundation, Czech Republic; The Danish Council for Independent Re-search | Natural Sciences, the VILLUM FONDEN and Danish National Research Foundation (DNRF),Denmark; Helsinki Institute of Physics (HIP), Finland; Commissariat à l’Energie Atomique (CEA) andInstitut National de Physique Nucléaire et de Physique des Particules (IN2P3) and Centre National de laRecherche Scientifique (CNRS), France; Bundesministerium für Bildung und Forschung (BMBF) andGSI Helmholtzzentrum für Schwerionenforschung GmbH, Germany; General Secretariat for Researchand Technology, Ministry of Education, Research and Religions, Greece; National Research, Devel-opment and Innovation Office, Hungary; Department of Atomic Energy Government of India (DAE),Department of Science and Technology, Government of India (DST), University Grants Commission,Government of India (UGC) and Council of Scientific and Industrial Research (CSIR), India; Indone-sian Institute of Science, Indonesia; Istituto Nazionale di Fisica Nucleare (INFN), Italy; Institute forInnovative Science and Technology , Nagasaki Institute of Applied Science (IIST), Japanese Ministryof Education, Culture, Sports, Science and Technology (MEXT) and Japan Society for the Promotionof Science (JSPS) KAKENHI, Japan; Consejo Nacional de Ciencia (CONACYT) y Tecnología, throughFondo de Cooperación Internacional en Ciencia y Tecnología (FONCICYT) and Dirección General deAsuntos del Personal Academico (DGAPA), Mexico; Nederlandse Organisatie voor WetenschappelijkOnderzoek (NWO), Netherlands; The Research Council of Norway, Norway; Commission on Scienceand Technology for Sustainable Development in the South (COMSATS), Pakistan; Pontificia Universi-dad Católica del Perú, Peru; Ministry of Science and Higher Education, National Science Centre andWUT ID-UB, Poland; Korea Institute of Science and Technology Information and National ResearchFoundation of Korea (NRF), Republic of Korea; Ministry of Education and Scientific Research, Instituteof Atomic Physics and Ministry of Research and Innovation and Institute of Atomic Physics, Romania;Joint Institute for Nuclear Research (JINR), Ministry of Education and Science of the Russian Federa-tion, National Research Centre Kurchatov Institute, Russian Science Foundation and Russian Foundationfor Basic Research, Russia; Ministry of Education, Science, Research and Sport of the Slovak Repub-lic, Slovakia; National Research Foundation of South Africa, South Africa; Swedish Research Council(VR) and Knut & Alice Wallenberg Foundation (KAW), Sweden; European Organization for NuclearResearch, Switzerland; Suranaree University of Technology (SUT), National Science and TechnologyDevelopment Agency (NSDTA) and Office of the Higher Education Commission under NRU project ofThailand, Thailand; Turkish Atomic Energy Agency (TAEK), Turkey; National Academy of Sciences ofUkraine, Ukraine; Science and Technology Facilities Council (STFC), United Kingdom; National Sci-ence Foundation of the United States of America (NSF) and United States Department of Energy, Officeof Nuclear Physics (DOE NP), United States of America. References [1] C. A. Bertulani, S. R. Klein, and J. Nystrand, “Physics of ultra-peripheral nuclear collisions”,
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Kileng , B. Kim , D. Kim , D.J. Kim , E.J. Kim , H. Kim , J. Kim ,J.S. Kim , J. Kim , J. Kim , J. Kim , M. Kim , S. Kim , T. Kim , S. Kirsch , I. Kisel , S. Kiselev ,A. Kisiel , J.L. Klay , J. Klein , , S. Klein , C. Klein-Bösing , M. Kleiner , T. Klemenz , A. Kluge ,A.G. Knospe , C. Kobdaj , M.K. Köhler , T. Kollegger , A. Kondratyev , N. Kondratyeva ,E. Kondratyuk , J. Konig , S.A. Konigstorfer , P.J. Konopka , , G. Kornakov , S.D. Koryciak ,L. Koska , O. Kovalenko , V. Kovalenko , M. Kowalski , I. Králik , A. Kravˇcáková , L. Kreis ,M. Krivda , , F. Krizek , K. Krizkova Gajdosova , M. Kroesen , M. Krüger , E. Kryshen ,M. Krzewicki , V. Kuˇcera , C. Kuhn , P.G. Kuijer , T. Kumaoka , L. Kumar , S. Kundu ,P. Kurashvili , A. Kurepin , A.B. Kurepin , A. Kuryakin , S. Kushpil , J. Kvapil , M.J. Kweon ,J.Y. Kwon , Y. Kwon , S.L. La Pointe , P. La Rocca , Y.S. Lai , A. Lakrathok , M. Lamanna ,R. Langoy , K. Lapidus , P. Larionov , E. Laudi , L. Lautner , R. Lavicka , T. Lazareva , R. Lea ,J. Lee , J. Lehrbach , R.C. Lemmon , I. León Monzón , E.D. Lesser , M. Lettrich , P. Lévai , X. Li ,X.L. Li , J. Lien , R. Lietava , B. Lim , S.H. Lim , V. Lindenstruth , A. Lindner , C. Lippmann ,A. Liu , J. Liu , I.M. Lofnes , V. Loginov , C. Loizides , P. Loncar , J.A. Lopez , X. Lopez , E. LópezTorres , J.R. Luhder , M. Lunardon , G. Luparello , Y.G. Ma , A. Maevskaya , M. Mager ,S.M. Mahmood , T. Mahmoud , A. Maire , R.D. Majka I , , M. Malaev , Q.W. Malik , L. Malinina IV , ,D. Mal’Kevich , N. Mallick , P. Malzacher , G. Mandaglio , , V. Manko , F. Manso , V. Manzari ,Y. Mao , J. Mareš , G.V. Margagliotti , A. Margotti , A. Marín , C. Markert , M. Marquard ,N.A. Martin , P. Martinengo , J.L. Martinez , M.I. Martínez , G. Martínez García , S. Masciocchi ,M. Masera , A. Masoni , L. Massacrier , A. Mastroserio , , A.M. Mathis , O. Matonoha ,P.F.T. Matuoka , A. Matyja , C. Mayer , A.L. Mazuecos , F. Mazzaschi , M. Mazzilli , ,M.A. Mazzoni , A.F. Mechler , F. Meddi , Y. Melikyan , A. Menchaca-Rocha , C. Mengke , ,E. Meninno , , A.S. Menon , M. Meres , S. Mhlanga , Y. Miake , L. Micheletti , L.C. Migliorin ,D.L. Mihaylov , K. Mikhaylov , , A.N. Mishra , , D. Mi´skowiec , A. Modak , N. Mohammadi ,A.P. Mohanty , B. Mohanty , M. Mohisin Khan , Z. Moravcova , C. Mordasini , D.A. Moreira DeGodoy , L.A.P. Moreno , I. Morozov , A. Morsch , T. Mrnjavac , V. Muccifora , E. Mudnic ,D. Mühlheim , S. Muhuri , J.D. Mulligan , A. Mulliri , M.G. Munhoz , R.H. Munzer , H. Murakami ,S. Murray , L. Musa , J. Musinsky , C.J. Myers , J.W. Myrcha , B. Naik , R. Nair , B.K. Nandi ,R. Nania , E. Nappi , M.U. Naru , A.F. Nassirpour , C. Nattrass , S. Nazarenko , A. Neagu ,L. Nellen , S.V. Nesbo , G. Neskovic , D. Nesterov , B.S. Nielsen , S. Nikolaev , S. Nikulin ,V. Nikulin , F. Noferini , S. Noh , P. Nomokonov , J. Norman , N. Novitzky , P. Nowakowski ,A. Nyanin , J. Nystrand , M. Ogino , A. Ohlson , J. Oleniacz , A.C. Oliveira Da Silva , M.H. Oliver ,A. Onnerstad , C. Oppedisano , A. Ortiz Velasquez , T. Osako , A. Oskarsson , J. Otwinowski ,K. Oyama , Y. Pachmayer , S. Padhan , D. Pagano , G. Pai´c , A. Palasciano , J. Pan ,S. Panebianco , P. Pareek , J. Park , J.E. Parkkila , S. Parmar , S.P. Pathak , B. Paul , J. Pazzini ,H. Pei , T. Peitzmann , X. Peng , L.G. Pereira , H. Pereira Da Costa , D. Peresunko , G.M. Perez ,S. Perrin , Y. Pestov , V. Petráˇcek , M. Petrovici , R.P. Pezzi , S. Piano , M. Pikna , P. Pillot ,O. Pinazza , , L. Pinsky , C. Pinto , S. Pisano , M. Płosko´n , M. Planinic , F. Pliquett ,M.G. Poghosyan , B. Polichtchouk , N. Poljak , A. Pop , S. Porteboeuf-Houssais , J. Porter ,V. Pozdniakov , S.K. Prasad , R. Preghenella , F. Prino , C.A. Pruneau , I. Pshenichnov , M. Puccio ,S. Qiu , L. Quaglia , R.E. Quishpe , S. Ragoni , A. Rakotozafindrabe , L. Ramello , F. Rami ,S.A.R. Ramirez , A.G.T. Ramos , R. Raniwala , S. Raniwala , S.S. Räsänen , R. Rath , I. Ravasenga ,K.F. Read , , A.R. Redelbach , K. Redlich V , , A. Rehman , P. Reichelt , F. Reidt , R. Renfordt ,Z. Rescakova , K. Reygers , A. Riabov , V. Riabov , T. Richert , , M. Richter , P. Riedler ,W. Riegler , F. Riggi , C. Ristea , S.P. Rode , M. Rodríguez Cahuantzi , K. Røed , R. Rogalev ,E. Rogochaya , T.S. Rogoschinski , D. Rohr , D. Röhrich , P.F. Rojas , P.S. Rokita , F. Ronchetti ,A. Rosano , , E.D. Rosas , A. Rossi , A. Rotondi , A. Roy , P. Roy , N. Rubini , O.V. Rueda ,R. Rui , B. Rumyantsev , A. Rustamov , E. Ryabinkin , Y. Ryabov , A. Rybicki , H. Rytkonen ,W. Rzesa , O.A.M. Saarimaki , R. Sadek , S. Sadovsky , J. Saetre , K. Šafaˇrík , S.K. Saha , S. Saha ,B. Sahoo , P. Sahoo , R. Sahoo , S. Sahoo , D. Sahu , P.K. Sahu , J. Saini , S. Sakai , S. Sambyal , | t | -dependence of coherent J / ψ photonuclear productionALICE Collaboration V. Samsonov I , , , D. Sarkar , N. Sarkar , P. Sarma , V.M. Sarti , M.H.P. Sas , , J. Schambach , ,H.S. Scheid , C. Schiaua , R. Schicker , A. Schmah , C. Schmidt , H.R. Schmidt , M.O. Schmidt ,M. Schmidt , N.V. Schmidt , , A.R. Schmier , R. Schotter , J. Schukraft , Y. Schutz , K. Schwarz ,K. Schweda , G. Scioli , E. Scomparin , J.E. Seger , Y. Sekiguchi , D. Sekihata , I. Selyuzhenkov , ,S. Senyukov , J.J. Seo , D. Serebryakov , L. Šerkšnyt˙e , A. Sevcenco , A. Shabanov , A. Shabetai ,R. Shahoyan , W. Shaikh , A. Shangaraev , A. Sharma , H. Sharma , M. Sharma , N. Sharma ,S. Sharma , O. Sheibani , A.I. Sheikh , K. Shigaki , M. Shimomura , S. Shirinkin , Q. Shou ,Y. Sibiriak , S. Siddhanta , T. Siemiarczuk , T.F.D. Silva , D. Silvermyr , G. Simatovic , G. Simonetti ,B. Singh , R. Singh , R. Singh , R. Singh , V.K. Singh , V. Singhal , T. Sinha , B. Sitar , M. Sitta ,T.B. Skaali , G. Skorodumovs , M. Slupecki , N. Smirnov , R.J.M. Snellings , C. Soncco , J. Song ,A. Songmoolnak , F. Soramel , S. Sorensen , I. Sputowska , J. Stachel , I. Stan , P.J. Steffanic ,S.F. Stiefelmaier , D. Stocco , M.M. Storetvedt , C.P. Stylianidis , A.A.P. Suaide , T. Sugitate ,C. Suire , M. Suljic , R. Sultanov , M. Šumbera , V. Sumberia , S. Sumowidagdo , S. Swain ,A. Szabo , I. Szarka , U. Tabassam , S.F. Taghavi , G. Taillepied , J. Takahashi , G.J. Tambave ,S. Tang , , Z. Tang , M. Tarhini , M.G. Tarzila , A. Tauro , G. Tejeda Muñoz , A. Telesca ,L. Terlizzi , C. Terrevoli , G. Tersimonov , S. Thakur , D. Thomas , R. Tieulent , A. Tikhonov ,A.R. Timmins , M. Tkacik , A. Toia , N. Topilskaya , M. Toppi , F. Torales-Acosta , S.R. Torres ,A. Trifiró , , S. Tripathy , T. Tripathy , S. Trogolo , G. Trombetta , V. Trubnikov , W.H. Trzaska ,T.P. Trzcinski , B.A. Trzeciak , A. Tumkin , R. Turrisi , T.S. Tveter , K. Ullaland , E.N. Umaka ,A. Uras , M. Urioni , G.L. Usai , M. Vala , N. Valle , S. Vallero , N. van der Kolk , L.V.R. vanDoremalen , M. van Leeuwen , P. Vande Vyvre , D. Varga , Z. Varga , M. Varga-Kofarago ,A. Vargas , M. Vasileiou , A. Vasiliev , O. Vázquez Doce , V. Vechernin , E. Vercellin , S. VergaraLimón , L. Vermunt , R. Vértesi , M. Verweij , L. Vickovic , Z. Vilakazi , O. Villalobos Baillie ,G. Vino , A. Vinogradov , T. Virgili , V. Vislavicius , A. Vodopyanov , B. Volkel , M.A. Völkl ,K. Voloshin , S.A. Voloshin , G. Volpe , B. von Haller , I. Vorobyev , D. Voscek , J. Vrláková ,B. Wagner , M. Weber , A. Wegrzynek , S.C. Wenzel , J.P. Wessels , J. Wiechula , J. Wikne ,G. Wilk , J. Wilkinson , G.A. Willems , E. Willsher , B. Windelband , M. Winn , W.E. Witt ,J.R. Wright , Y. Wu , R. Xu , S. Yalcin , Y. Yamaguchi , K. Yamakawa , S. Yang , S. Yano , ,Z. Yin , H. Yokoyama , I.-K. Yoo , J.H. Yoon , S. Yuan , A. Yuncu , V. Yurchenko , V. Zaccolo ,A. Zaman , C. Zampolli , H.J.C. Zanoli , N. Zardoshti , A. Zarochentsev , P. Závada , N. Zaviyalov ,H. Zbroszczyk , M. Zhalov , S. Zhang , X. Zhang , Y. Zhang , V. Zherebchevskii , Y. Zhi , D. Zhou ,Y. Zhou , J. Zhu , , Y. Zhu , A. Zichichi , G. Zinovjev , N. Zurlo Affiliation notes I Deceased II Also at: Italian National Agency for New Technologies, Energy and Sustainable Economic Development(ENEA), Bologna, Italy
III
Also at: Dipartimento DET del Politecnico di Torino, Turin, Italy IV Also at: M.V. Lomonosov Moscow State University, D.V. Skobeltsyn Institute of Nuclear, Physics, Moscow,Russia V Also at: Institute of Theoretical Physics, University of Wroclaw, Poland
Collaboration Institutes A.I. Alikhanyan National Science Laboratory (Yerevan Physics Institute) Foundation, Yerevan, Armenia AGH University of Science and Technology, Cracow, Poland Bogolyubov Institute for Theoretical Physics, National Academy of Sciences of Ukraine, Kiev, Ukraine Bose Institute, Department of Physics and Centre for Astroparticle Physics and Space Science (CAPSS),Kolkata, India Budker Institute for Nuclear Physics, Novosibirsk, Russia California Polytechnic State University, San Luis Obispo, California, United States Central China Normal University, Wuhan, China Centro de Aplicaciones Tecnológicas y Desarrollo Nuclear (CEADEN), Havana, Cuba Centro de Investigación y de Estudios Avanzados (CINVESTAV), Mexico City and Mérida, Mexico Chicago State University, Chicago, Illinois, United States | t | -dependence of coherent J / ψ photonuclear productionALICE Collaboration China Institute of Atomic Energy, Beijing, China Chungbuk National University, Cheongju, Republic of Korea Comenius University Bratislava, Faculty of Mathematics, Physics and Informatics, Bratislava, Slovakia COMSATS University Islamabad, Islamabad, Pakistan Creighton University, Omaha, Nebraska, United States Department of Physics, Aligarh Muslim University, Aligarh, India Department of Physics, Pusan National University, Pusan, Republic of Korea Department of Physics, Sejong University, Seoul, Republic of Korea Department of Physics, University of California, Berkeley, California, United States Department of Physics, University of Oslo, Oslo, Norway Department of Physics and Technology, University of Bergen, Bergen, Norway Dipartimento di Fisica dell’Università ’La Sapienza’ and Sezione INFN, Rome, Italy Dipartimento di Fisica dell’Università and Sezione INFN, Cagliari, Italy Dipartimento di Fisica dell’Università and Sezione INFN, Trieste, Italy Dipartimento di Fisica dell’Università and Sezione INFN, Turin, Italy Dipartimento di Fisica e Astronomia dell’Università and Sezione INFN, Bologna, Italy Dipartimento di Fisica e Astronomia dell’Università and Sezione INFN, Catania, Italy Dipartimento di Fisica e Astronomia dell’Università and Sezione INFN, Padova, Italy Dipartimento di Fisica e Nucleare e Teorica, Università di Pavia and Sezione INFN, Pavia, Italy Dipartimento di Fisica ‘E.R. Caianiello’ dell’Università and Gruppo Collegato INFN, Salerno, Italy Dipartimento DISAT del Politecnico and Sezione INFN, Turin, Italy Dipartimento di Scienze e Innovazione Tecnologica dell’Università del Piemonte Orientale and INFN Sezionedi Torino, Alessandria, Italy Dipartimento di Scienze MIFT, Università di Messina, Messina, Italy Dipartimento Interateneo di Fisica ‘M. Merlin’ and Sezione INFN, Bari, Italy European Organization for Nuclear Research (CERN), Geneva, Switzerland Faculty of Electrical Engineering, Mechanical Engineering and Naval Architecture, University of Split, Split,Croatia Faculty of Engineering and Science, Western Norway University of Applied Sciences, Bergen, Norway Faculty of Nuclear Sciences and Physical Engineering, Czech Technical University in Prague, Prague, CzechRepublic Faculty of Science, P.J. Šafárik University, Košice, Slovakia Frankfurt Institute for Advanced Studies, Johann Wolfgang Goethe-Universität Frankfurt, Frankfurt, Germany Fudan University, Shanghai, China Gangneung-Wonju National University, Gangneung, Republic of Korea Gauhati University, Department of Physics, Guwahati, India Helmholtz-Institut für Strahlen- und Kernphysik, Rheinische Friedrich-Wilhelms-Universität Bonn, Bonn,Germany Helsinki Institute of Physics (HIP), Helsinki, Finland High Energy Physics Group, Universidad Autónoma de Puebla, Puebla, Mexico Hiroshima University, Hiroshima, Japan Hochschule Worms, Zentrum für Technologietransfer und Telekommunikation (ZTT), Worms, Germany Horia Hulubei National Institute of Physics and Nuclear Engineering, Bucharest, Romania Indian Institute of Technology Bombay (IIT), Mumbai, India Indian Institute of Technology Indore, Indore, India Indonesian Institute of Sciences, Jakarta, Indonesia INFN, Laboratori Nazionali di Frascati, Frascati, Italy INFN, Sezione di Bari, Bari, Italy INFN, Sezione di Bologna, Bologna, Italy INFN, Sezione di Cagliari, Cagliari, Italy INFN, Sezione di Catania, Catania, Italy INFN, Sezione di Padova, Padova, Italy INFN, Sezione di Roma, Rome, Italy INFN, Sezione di Torino, Turin, Italy INFN, Sezione di Trieste, Trieste, Italy Inha University, Incheon, Republic of Korea | t | -dependence of coherent J / ψ photonuclear productionALICE Collaboration Institute for Gravitational and Subatomic Physics (GRASP), Utrecht University/Nikhef, Utrecht, Netherlands Institute for Nuclear Research, Academy of Sciences, Moscow, Russia Institute of Experimental Physics, Slovak Academy of Sciences, Košice, Slovakia Institute of Physics, Homi Bhabha National Institute, Bhubaneswar, India Institute of Physics of the Czech Academy of Sciences, Prague, Czech Republic Institute of Space Science (ISS), Bucharest, Romania Institut für Kernphysik, Johann Wolfgang Goethe-Universität Frankfurt, Frankfurt, Germany Instituto de Ciencias Nucleares, Universidad Nacional Autónoma de México, Mexico City, Mexico Instituto de Física, Universidade Federal do Rio Grande do Sul (UFRGS), Porto Alegre, Brazil Instituto de Física, Universidad Nacional Autónoma de México, Mexico City, Mexico iThemba LABS, National Research Foundation, Somerset West, South Africa Jeonbuk National University, Jeonju, Republic of Korea Johann-Wolfgang-Goethe Universität Frankfurt Institut für Informatik, Fachbereich Informatik undMathematik, Frankfurt, Germany Joint Institute for Nuclear Research (JINR), Dubna, Russia Korea Institute of Science and Technology Information, Daejeon, Republic of Korea KTO Karatay University, Konya, Turkey Laboratoire de Physique des 2 Infinis, Irène Joliot-Curie, Orsay, France Laboratoire de Physique Subatomique et de Cosmologie, Université Grenoble-Alpes, CNRS-IN2P3, Grenoble,France Lawrence Berkeley National Laboratory, Berkeley, California, United States Lund University Department of Physics, Division of Particle Physics, Lund, Sweden Moscow Institute for Physics and Technology, Moscow, Russia Nagasaki Institute of Applied Science, Nagasaki, Japan Nara Women’s University (NWU), Nara, Japan National and Kapodistrian University of Athens, School of Science, Department of Physics , Athens, Greece National Centre for Nuclear Research, Warsaw, Poland National Institute of Science Education and Research, Homi Bhabha National Institute, Jatni, India National Nuclear Research Center, Baku, Azerbaijan National Research Centre Kurchatov Institute, Moscow, Russia Niels Bohr Institute, University of Copenhagen, Copenhagen, Denmark Nikhef, National institute for subatomic physics, Amsterdam, Netherlands NRC Kurchatov Institute IHEP, Protvino, Russia NRC «Kurchatov»Institute - ITEP, Moscow, Russia NRNU Moscow Engineering Physics Institute, Moscow, Russia Nuclear Physics Group, STFC Daresbury Laboratory, Daresbury, United Kingdom Nuclear Physics Institute of the Czech Academy of Sciences, ˇRež u Prahy, Czech Republic Oak Ridge National Laboratory, Oak Ridge, Tennessee, United States Ohio State University, Columbus, Ohio, United States
Petersburg Nuclear Physics Institute, Gatchina, Russia
Physics department, Faculty of science, University of Zagreb, Zagreb, Croatia
Physics Department, Panjab University, Chandigarh, India
Physics Department, University of Jammu, Jammu, India
Physics Department, University of Rajasthan, Jaipur, India
Physikalisches Institut, Eberhard-Karls-Universität Tübingen, Tübingen, Germany
Physikalisches Institut, Ruprecht-Karls-Universität Heidelberg, Heidelberg, Germany
Physik Department, Technische Universität München, Munich, Germany
Politecnico di Bari and Sezione INFN, Bari, Italy
Research Division and ExtreMe Matter Institute EMMI, GSI Helmholtzzentrum für SchwerionenforschungGmbH, Darmstadt, Germany
Rudjer Boškovi´c Institute, Zagreb, Croatia
Russian Federal Nuclear Center (VNIIEF), Sarov, Russia
Saha Institute of Nuclear Physics, Homi Bhabha National Institute, Kolkata, India
School of Physics and Astronomy, University of Birmingham, Birmingham, United Kingdom
Sección Física, Departamento de Ciencias, Pontificia Universidad Católica del Perú, Lima, Peru
St. Petersburg State University, St. Petersburg, Russia | t | -dependence of coherent J / ψ photonuclear productionALICE Collaboration Stefan Meyer Institut für Subatomare Physik (SMI), Vienna, Austria
SUBATECH, IMT Atlantique, Université de Nantes, CNRS-IN2P3, Nantes, France
Suranaree University of Technology, Nakhon Ratchasima, Thailand
Technical University of Košice, Košice, Slovakia
The Henryk Niewodniczanski Institute of Nuclear Physics, Polish Academy of Sciences, Cracow, Poland
The University of Texas at Austin, Austin, Texas, United States
Universidad Autónoma de Sinaloa, Culiacán, Mexico
Universidade de São Paulo (USP), São Paulo, Brazil
Universidade Estadual de Campinas (UNICAMP), Campinas, Brazil
Universidade Federal do ABC, Santo Andre, Brazil
University of Cape Town, Cape Town, South Africa
University of Houston, Houston, Texas, United States
University of Jyväskylä, Jyväskylä, Finland
University of Liverpool, Liverpool, United Kingdom
University of Science and Technology of China, Hefei, China
University of South-Eastern Norway, Tonsberg, Norway
University of Tennessee, Knoxville, Tennessee, United States
University of the Witwatersrand, Johannesburg, South Africa
University of Tokyo, Tokyo, Japan
University of Tsukuba, Tsukuba, Japan
Université Clermont Auvergne, CNRS/IN2P3, LPC, Clermont-Ferrand, France
Université de Lyon, CNRS/IN2P3, Institut de Physique des 2 Infinis de Lyon , Lyon, France
Université de Strasbourg, CNRS, IPHC UMR 7178, F-67000 Strasbourg, France, Strasbourg, France
Université Paris-Saclay Centre d’Etudes de Saclay (CEA), IRFU, Départment de Physique Nucléaire (DPhN),Saclay, France
Università degli Studi di Foggia, Foggia, Italy
Università di Brescia and Sezione INFN, Brescia, Italy
Variable Energy Cyclotron Centre, Homi Bhabha National Institute, Kolkata, India
Warsaw University of Technology, Warsaw, Poland
Wayne State University, Detroit, Michigan, United States
Westfälische Wilhelms-Universität Münster, Institut für Kernphysik, Münster, Germany
Wigner Research Centre for Physics, Budapest, Hungary
Yale University, New Haven, Connecticut, United States