aa r X i v : . [ h e p - e x ] O c t Proceedings of the CHARM 2007 Workshop, Ithaca, NY, August 5-8, 2007 Charm Meson Spectroscopy at B A B AR and CLEO-c A. ZghicheFrom the B A B AR Collaboration
Laboratoire de Physique des Particules,CNRS-IN2P3, F-74941 Annecy-le-Vieux - France
In this mini-review we report on the most recent progress in charm meson spectroscopy. We discuss the precisionmeasurements performed by the B A B AR and CLEO-c experiments in the non strange charm meson part and wepresent the newly discovered strange charmed meson excited states.
1. Introduction
During the last few years many new D , D s , charmo-nium, and charmed baryon excited states have beendiscovered. Some of these states were not expectedtheoretically; their masses, widths, quantum numbers,and decay modes did not fit the existing spectroscopicclassification, which was based mostly on potentialmodel calculations. The theoretical models had to beimproved and new approaches have been developedto explain the data; the possibility of a non-quark-antiquark interpretation of these states has also beenwidely discussed. Charmonium, and charmed baryonexcited states results are discussed elsewhere in theseproceedings. In this report an overview of recent re-sults on non strange charm mesons production is pre-sented. Then, recent results on excited D sJ mesonproduction will be presented and their behavior willbe discussed.
2. Non Strange Charm Mesons2.1. Measurement of the AbsoluteBranching Fractions B → Dπ, D ∗ π, D ∗∗ π with a Missing Mass Method Our understanding of hadronic B -meson decayshas improved considerably during the past few yearswith the development of models based on the HeavyQuark Effective Theory (HQET), where collinear [1,2] or k T [3, 4] factorization theorems are consid-ered. Models such as the QCD-improved Factoriza-tion (QCDF) [5, 6] and the Soft Collinear EffectiveTheory (SCET) [1, 7] use the collinear factorization,while the perturbative QCD (pQCD) approach [8, 9]uses the k T factorization. In these models the am-plitude of the B → D ( ∗ ) π two-body decay carries in-formation about the difference δ between the strong-interaction phases of the two isospin amplitudes A / and A / that contribute [10, 11]. A non-zero value of δ provides a measure of the departure from the heavy-quark limit and the importance of the final-state inter-actions in the D ( ∗ ) π system. With the measurementsby the B A B AR [12] and BELLE [13] experiments of the color-suppressed B decay B → D ( ∗ )0 π provid-ing evidence for a sizeable value of δ , an improvedmeasurement of the color-favored decay amplitudes( B − → D ( ∗ )0 π − and B → D ( ∗ )+ π − ) is of renewedinterest. In addition, the study of B decays into D , D ∗ , and D ∗∗ mesons will allow tests of the spin sym-metry [14, 15, 16, 17] imbedded in HQET and of non-factorizable corrections [18] that have been assumedto be negligible in the case of the excited states D ∗∗ [19].A measurement of the branching fractions is pre-sented for the decays B − → D π − , D ∗ π − , D ∗∗ π − and B → D + π − , D ∗ + π − , D ∗∗ + π − [20] with a miss-ing mass method, based on a sample of 231 million Υ (4 S ) → BB pairs collected by the B A B AR detectorat the PEP-II e + e − collider. One of the B mesons isfully reconstructed and the other one decays to a re-constructed π and a companion charmed meson iden-tified by its recoil mass, inferred by the kinematics ofthe two body B decay. This method, compared to theprevious exclusive measurements [21], does not implythat the Υ (4 S ) decays into B + and B with equalrates, nor rely on the D , D ∗ , or D ∗∗ decay branch-ing fractions. The number of fully reconstructed Bmesons B rec ′ d is extracted from a fit to its mass dis-tribution. In the decay Υ (4 S ) → B rec ′ d B X π where B X π is the recoiling B which decays into π − X , the in-variant mass of the X system is derived from the miss-ing 4-momentum p X applying the energy-momentumconservation: p X = p Υ (4 S ) − p B rec ′ d − p π − . The 4-momentum of the Υ (4 S ), p Υ (4 S ) , is computedfrom the beam energies and p π and p B rec ′ d are themeasured 4-momenta of the pion and of the recon-structed B rec ′ d , respectively. The B rec ′ d energy isconstrained by the beam energies. The B → Dπ − , B → D ∗ π − , or B → D ∗∗ π − signal yields peak at the D , D ∗ , and D ∗∗ masses in the missing mass spectrum,respectively. The signal yield of the different modes,is extracted from the missing mass spectra. The Dπ and D ∗ π signal yields are extracted by a χ fit tothe background subtracted missing mass distributionin the range 1 . − .
20 GeV /c . The D ∗∗ yield isobtained by counting the candidates in excess in themissing mass range 2 . − . /c . This range is Proceedings of the CHARM 2007 Workshop, Ithaca, NY, August 5-8, 2007 chosen in order to keep most of the excess and nofurther assumption on D ∗∗ resonance composition ismade. The following branching fractions [22] are mea-sured: B ( B − → D π − ) = (4 . ± . ± . × − B ( B − → D ∗ π − ) = (5 . ± . ± . × − B ( B − → D ∗∗ π − ) = (5 . ± . ± . × − B ( B → D + π − ) = (3 . ± . ± . × − B ( B → D ∗ + π − ) = (2 . ± . ± . × − B ( B → D ∗∗ + π − ) = (2 . ± . ± . × − and the branching ratios: B ( B − → D ∗ π − ) / B ( B − → D π − ) = 1 . ± . ± . B ( B − → D ∗∗ π − ) / B ( B − → D π − ) = 1 . ± . ± . B ( B → D ∗ + π − ) / B ( B → D + π − ) = 0 . ± . ± . B ( B → D ∗∗ + π − ) / B ( B → D + π − ) = 0 . ± . ± . D massby CLEO-c The D (c u ) and D ± (d c ,c d ) mesons form theground states of the open charm system. The knowl-edge of their masses is important for its own sake,but a precision determination of the D mass has be-come more important because of the recent discoveryof a narrow state known as X(3872) [24, 25, 26, 27].Many different theoretical models have been pro-posed [28, 29, 30, 31] to explain the nature of thisstate, whose present average of measured massesis M ( X ) = 3871 . ± . D and D ∗ mesons [31]. This suggestion arises mainly fromthe closeness of M [ X (3872)] to M ( D ) + M ( D ∗ ) =2 M ( D ) + [ M ( D ∗ ) − M ( D )] = 2(1864 . ± .
0) +(142 . ± .
07) MeV = 3870 . ± . D mass, M ( D ) = 1864 . ± . E b [X(3872)]=M( D )+M( D ∗ )- M[X(3872)]= − . ± . D and D ∗ , its ± . D and X(3872) with much improved precision toreach a firm conclusion. Recently, CLEO-c reporteda precision measurement of the D mass, and pro-vided a more constrained value of the binding energyof X(3872) as a molecule. Several earlier measure-ments of the D mass exist. The PDG [32] result-ing average D mass is based on the measured D masses as M( D ) AV G = 1864 . ± . D ) F IT = 1864 . ± . D ± , D , D ± s , D ∗± , D ∗ , and D ∗± s masses and mass dif-ferences. In its recent measurement, CLEO-c ana-lyzes 281 pb − of e + e − annihilation data taken atthe Ψ(3770) resonance at the Cornell Electron StorageRing (CESR) with the CLEO-c detector to measurethe D mass using the reaction Ψ(3770) → D D ,with D → K S Φ, K S → π + π − and Φ → K + K − . Thechoice of the D → K S Φ mode is motivated by the de-termination of the D mass not depending on the pre-cision of the determination of the beam energy. SinceM(Φ)+M( K S )=1517 MeV is a substantial fraction ofM( D ), the final state particles have small momentaand the uncertainty in their measurement makes asmall contribution to the total uncertainty in M( D ).This consideration favors D → K S Φ over the moreprolific decays D → K − π + and D → K − π + π − π + in which the decay particles have considerably largermomenta and therefore greater sensitivity to the mea-surement uncertainties. An additional advantage ofthe D → K S Φ reaction is that in fitting for M( D )the mass of K S can be constrained to its value whichis known with precision [32]. The final result of thismeasurement is M( D ) = 1864.847 ± ± D )=1864.847 ± D ) leads to M( D D ∗ )=3871.81 ± D D ∗ molecule is E b = (3871.81 ± ± ± D D ∗ molecule [31]. The error in the binding energyis now dominated by the error in the X(3872) massmeasurement, which will hopefully improve as the re-sults from the analysis of larger luminosity data fromvarious experiments become available. This analysisis published [33].
3. Strange charm mesons
Much of the theoretical work on the c ¯ s system hasbeen performed in the limit of heavy c quark mass us-ing potential models [34, 35, 36, 37] that treat the c ¯ s system much like a hydrogen atom. Prior to the dis-covery of the D ∗ sJ (2317) + meson, such models weresuccessful at explaining the masses of all known D and D s states and even predicting, to good accu-racy, the masses of many D mesons (including the D s (2536) + and D s (2573) + ) before they were ob-served (see Fig. 1). Several of the predicted D s stateswere not confirmed experimentally, notably the low-est mass J P = 0 + state (at around 2.48 GeV /c ) andthe second lowest mass J P = 1 + state (at around roceedings of the CHARM 2007 Workshop, Ithaca, NY, August 5-8, 2007 Figure 1: The c ¯ s meson spectrum, as predicted by Godfreyand Isgur [34] (solid lines) and Di Pierro and Eichten [37](dashed lines) and as observed by experiment (points).The DK and D ∗ K mass thresholds are indicated by thehorizontal lines spanning the width of the plot. /c ). Since the predicted widths of thesetwo states were large, they would be hard to observe,and thus the lack of experimental evidence was not aconcern. D ∗ sJ (2317) + and D sJ (2460) + The D ∗ sJ (2317) + meson has been observed in thedecay D ∗ sJ (2317) + → D + s π [38, 39, 40, 41, 42]. Themass is measured to be around 2 .
32 GeV /c , whichis below the DK threshold. Thus, this particle isforced to decay either electromagnetically, of whichthere is no experimental evidence, or through the ob-served isospin-violating D + s π strong decay. The in-trinsic width is small enough that only upper limitshave been measured (the best limit previous to thisanalysis being Γ < . D ∗ sJ (2317) + is the missing 0 + c ¯ s meson state, the narrow width could be explainedby the lack of an isospin-conserving strong decay chan-nel. The low mass (160 MeV /c below expectations)is more surprising and has led to the speculation thatthe D ∗ sJ (2317) + does not belong to the D + s mesonfamily at all but is instead some type of exotic parti-cle, such as a four-quark state [43].The D sJ (2460) + meson has been observed decay-ing to D + s π γ [38, 39, 40, 41, 42], D + s π + π − [40], and D + s γ [40, 41, 42]. The intrinsic width is small enoughthat only upper limits have been measured (the bestlimit previous to this analysis being Γ < . D + s γ de-cay implies a spin of at least one, and so it is naturalto assume that the D sJ (2460) + is the missing 1 + c ¯ s meson state. Like the D ∗ sJ (2317) + , the D sJ (2460) + is substantially lower in mass than predicted for thenormal c ¯ s meson. This suggests that a similar mech-anism is deflating the masses of both mesons, or thatboth the states belong to the same family of exoticparticles.The spin-parity of the D ∗ sJ (2317) + and D sJ (2460) + mesons has not been firmly established. Thedecay mode of the D ∗ sJ (2317) + alone implies aspin-parity assignment from the natural J P series { + , − , + , . . . } , assuming parity conservation. Be-cause of the low mass, the assignment J P = 0 + seemsmost reasonable, although experimental data have notruled out higher spin. It is not clear whether elec-tromagnetic decays such as D ∗ s (2112) + γ can competewith the strong decay to D + s π , even with isospin vio-lation. Thus, the absence of experimental evidence forradiative decays such as D ∗ sJ (2317) + → D ∗ s (2112) + γ is not conclusive.Experimental evidence for the spin-parity of the D sJ (2460) + meson is somewhat stronger. The obser-vation of the decay to D + s γ alone rules out J = 0. De-cay distribution studies in B → D sJ (2460) + D ( ∗ ) − s [41,42] favor the assignment J = 1. Decays to either D + s π , D K + , or D + K would be favored if they wereallowed. Since these decay channels are not observed,this suggests, when combined with the other obser-vations, the assignment J P = 1 + . In this case, thedecay to D ∗ sJ (2317) + γ is allowed, but it may be smallin comparison to the D + s γ decay mode.An updated analysis of the D ∗ sJ (2317) + and D sJ (2460) + mesons using 232 fb − of e + e − → c ¯ c datais presented here. Established signals from the de-cay D ∗ sJ (2317) + → D + s π and D sJ (2460) + → D + s π γ , D + s γ , and D + s π + π − are confirmed. A detailed analy-sis of invariant mass distributions of these final statesincluding consideration of the background introducedby reflections of other c ¯ s decays produces the followingmass values: m ( D ∗ sJ (2317) + ) = (2319 . ± . ± .
4) MeV /c m ( D sJ (2460) + ) = (2460 . ± . ± .
8) MeV /c , where the first error is statistical and the second sys-tematic. Upper 95% CL limits of Γ < . < . D ∗ sJ (2317) + and D sJ (2460) + widths. All results areconsistent with previous measurements.The following final states are investigated: D + s π , D + s γ , D ∗ s (2112) + π , D ∗ sJ (2317) + γ , D + s π π , D ∗ s (2112) + γ , D + s γγ , D + s π ± , and D + s π + π − . Nostatistically significant evidence of new decay modesis observed. The following branching ratios aremeasured: B ( D sJ (2460) + → D + s γ ) B ( D sJ (2460) + → D + s π γ ) = 0 . ± . ± . B ( D sJ (2460) + → D + s π + π − ) B ( D sJ (2460) + → D + s π γ ) = 0 . ± . ± . , Proceedings of the CHARM 2007 Workshop, Ithaca, NY, August 5-8, 2007 where the first error is statistical and the second sys-tematic. The data are consistent with the decay D sJ (2460) + → D + s π γ proceeding entirely through D ∗ s (2112) + π .Since the results presented here are consistent with J P = 0 + and J P = 1 + spin-parity assignments for the D ∗ sJ (2317) + and D sJ (2460) + mesons, these two statesremain viable candidates for the lowest lying p -wave c ¯ s mesons. The lack of evidence for some radiativedecays, in particular D ∗ sJ (2317) + → D ∗ s (2112) + γ and D sJ (2460) + → D ∗ s (2112) + γ , are in contradiction withthis hypothesis according to some calculations, butlarge theoretical uncertainties remain. No state nearthe D ∗ sJ (2317) + mass is observed decaying to D + s π ± .If charged or neutral partners to the D ∗ sJ (2317) + exist(as would be expected if the D ∗ sJ (2317) + is a four-quark state), some mechanism is required to suppresstheir production in e + e − collisions. This analysis isrealized in inclusive c ¯ c production using 232 fb − ofdata collected by the B A B AR experiment near √ s =10 . D s (2536) + Case
For a complete understanding of the charmedstrange meson spectrum, a comprehensive knowledgeof the parameters of all known D + s mesons is manda-tory. In this part of the presentation, a precision mea-surement of the mass and the decay width of the me-son D s (2536) + is presented. The mass is currentlyreported by the PDG with a precision of 0 . /c ,while only an upper limit of 2 . /c is given forthe decay width [32]. These values are based on mea-surements with 20 times fewer reconstructed D + s can-didates compared to this one. The B A B AR experiment,in addition to its excellent tracking and vertexing ca-pabilities, provides a rich source of charmed hadrons,enabling an analysis of the D + s with high statisticsand small errors.Since the uncertainty of the D ∗ + mass is large(0 . /c [32]), a measurement of the mass differ-ence defined by∆ m ( D + s ) = m ( D + s ) − m ( D ∗ + ) − m ( K S ) , is performed. Additionally, due to the correlationbetween the masses, the D + s signal in the mass dif-ference spectrum is much more narrow than the onefrom the D + s mass spectrum alone leading to a highprecision measurement of the mass and the decaywidth of the meson D s (2536) + using the decay mode D + s → D ∗ + K S . The mass difference between D + s and D ∗ + K S for the two reconstructed decay modes ismeasured to be∆ µ ( D + s ) K π = 27 . ± . ± .
031 MeV /c ,∆ µ ( D + s ) K π = 27 . ± . ± .
043 MeV /c , with the first error denoting the statistical uncertaintyand the second one the systematic uncertainty. Theseresults correspond to a relative error of 0 .
15% for themass difference. This lies within the range of precisionachievable with the B A B AR detector: the J/ψ mass hasbeen reconstructed with a relative error of 0 .
05% [46].Combining the results, while taking the systematicerrors including the uncertainties of the D ∗ + mass( ± . /c ) and of the K S mass ( ± .
022 MeV /c )into account, yields a final value for the D + s mass of m ( D + s ) = 2534 . ± . ± .
40 MeV /c ,while the PDG value for the mass is given as 2535 . ± . ± .
50 MeV /c . The error on the measured D + s mass is dominated by the uncertainty of the D ∗ + mass. The mass difference between the D + s and the D ∗ + follows from these results as∆ m = m ( D + s ) − m ( D ∗ + ) =524 . ± . ± .
04 MeV /c .The decay width is measured to beΓ( D + s ) K π = 1 . ± . ± .
131 MeV /c ,Γ( D + s ) K π = 0 . ± . ± .
119 MeV /c .The final combined value for decay width isΓ( D + s ) = 1 . ± . ± .
12 MeV /c .The result for the mass difference ∆ m = m ( D + s ) − m ( D ∗ + ) represents an improvement in precision by afactor of 14 compared with the current PDG valueof 525 . ± . ± . /c . It deviates by 1 σ fromthe larger PDG value. The precision achieved iscomparable with other recent high precision analysesperformed at B A B AR like the Λ c mass measurement( m ( Λ c ) = 2286 . ± . ± .
14 MeV /c ) [47]. Fur-thermore, this analysis presents for the first time adirect measurement of the D + s decay width with smallerrors rather than just an upper limit, which is cur-rently stated by the PDG as 2 . /c . This anal-ysis is also realized in inclusive c ¯ c production using232 fb − of data collected by the B A B AR experimentnear √ s = 10 . D s (2573) + and New StrangeCharmed Mesons Here, a new cs state and a broad structure ob-served in the decay channels D K + and D + K S are re-ported. This analysis is based on a 240 fb − inclusive c ¯ c data sample recorded near the Υ (4 S ) resonance bythe B A B AR detector at the PEP-II asymmetric-energy e + e − storage rings.Three inclusive processes [20] are reconstructed: e + e − → D K + X, D → K − π + (1) e + e − → D K + X, D → K − π + π (2) e + e − → D + K S X, D + → K − π + π + , K S → π + π − (3) roceedings of the CHARM 2007 Workshop, Ithaca, NY, August 5-8, 2007 Figure 2: The DK invariant mass distributions for (a) D K − π + K + , (b) D K − π + π K + and (c) D + K − π + π + K s . The shadedhistograms are for the D -mass sideband regions. The dotted histogram in (a) is from e + e − → c ¯ c Monte Carlo simulationsincorporating previously known D s states with an arbitrary normalization. The insets show an expanded view of the2.86 GeV /c region. The solid curves are the fitted background threshold functions from the three separate fits. Selecting events in the D signal regions, Fig. 2 showsthe D K + invariant mass distributions for channels(1) and (2), and the D + K S invariant mass distribu-tion for channel (3). To improve mass resolution, thenominal D mass and the reconstructed 3-momentumare used to calculate the D energy for channels (1) and(3). Since channel (2) has a poorer D resolution, each K − π + π candidate is kinematically fit with a D massconstraint and a χ probability greater than 0.1% isrequired.The fraction of events having more than one DK combination per event is 0.9% for channels (1) and(3) and 3.4% for channel (2). In the following, theterm reflection will be used to describe enhancementsproduced by two or three body decays of narrow res-onances where one of the decay products is missed.The three mass spectra in Fig. 2 present similarfeatures: • A single bin peak at 2.4 GeV /c due to a re-flection from the decays of the D s (2536) + to D ∗ K + or D ∗ + K S in which the π or γ fromthe D ∗ decay is missed. This state, if J P = 1 + ,cannot decay to DK . • A prominent narrow signal due to the D s (2573) + . • A broad structure peaking at a mass of approx-imately 2.7 GeV /c . • An enhancement around 2.86 GeV /c . This canbe seen better in the expanded views shown in the insets of Fig. 2.Different background sources are examined: com-binatorial, possible reflections from D ∗ decays, andparticle misidentification.Backgrounds come both from events in which thecandidate D meson is correctly identified and fromevents in which it is not. The first case can be studiedcombining a reconstructed D meson with a kaon fromanother ¯ D meson in the same event, using data withfully reconstructed D ¯ D pairs or Monte Carlo simu-lations. No signal near 2.7 or 2.86 GeV /c is seenin the DK mass plots for these events. The secondcase can be studied using the D mass sidebands. Theshaded regions in Fig. 2 show the DK mass spectrafor events in the D sideband regions normalized to theestimated background in the signal region. No promi-nent structure is visible in the sideband mass spectra.The dotted histogram in (a) is from e + e − → c ¯ c MonteCarlo simulations incorporating previously known D s states with an arbitrary normalization.The possibility that the features at 2.7 and2.86 GeV /c could be a reflection from D ∗ or otherhigher mass resonances is considered. Candidate DK pairs where the D is a D ∗ -decay product are iden-tified by forming Dπ and Dγ combinations and re-quiring the invariant-mass difference between one ofthose combinations and the D to be within ± σ ofthe known D ∗ − D mass difference. No signal near 2.7or 2.86 GeV /c is seen in the DK mass plots for theseevents. Events belonging to these possible reflections(except for the D ∗ → D γ events, which could notbe isolated cleanly) have been removed from the mass Proceedings of the CHARM 2007 Workshop, Ithaca, NY, August 5-8, 2007 distributions shown in Fig. 2 (corresponding to ≈ D K − π + K + , D K − π + π K + ,and D + K − π + π + K s invariant mass distributions in the2.86 GeV /c mass region. Fig. 3(d) shows the sum ofthe three mass spectra.In the following, the structure in the 2.86 GeV /c mass region is labelled D sJ (2860) + and the one in the2.7 GeV /c mass region is labelled X (2690) + . Thethree DK mass spectra shown in Fig. 2 from 2.42GeV /c to 3.1 GeV /c (excluding the D s (2536) + re-flection) are first fitted separately using a binned χ minimization. The background for the three DK massdistributions is described by a threshold function:( m − m th ) α e − βm − γm − δm where m th = m D + m K . Afit to the Monte Carlo distribution shown in Fig. 2(a)using this background expression and one spin-2 rela-tivistic Breit-Wigner for the D s (2573) + gives a good32 % χ probability. In the fit to the data, the D s (2573) + and D sJ (2860) + peaks are described withrelativistic Breit-Wigner lineshapes where spin-2 is as-sumed for the D s (2573) + and spin 0 is used for the D sJ (2860) + . The D sJ (2860) + parameters are foundinsensitive to the choice of the spin. The best descrip-tion of the X (2690) + structure is obtained using aGaussian distribution. The fits give consistent valuesfor the parameters of the three structures.When the three mass distributions of Fig. 2 are fit-ted simultaneously, the resulting resonance parame-ters are also found consistent with those obtained withprevious separate fits. For D s (2573) + resonance,mass and width are: m ( D s (2573) + ) = (2572 . ± . ± .
0) MeV /c Γ( D s (2573) + ) = (27 . ± . ± .
6) MeV /c , where the first errors are statistical and the secondsystematic. For the new states, the following valuesare obtained: m ( D sJ (2860) + ) = (2856 . ± . ± .
0) MeV /c Γ( D sJ (2860) + ) = (47 ± ±
10) MeV /c .m ( X (2690) + ) = (2688 ± ±
3) MeV /c Γ( X (2690) + ) = (112 ± ±
36) MeV /c . In summary, in 240 fb − of data collected by the B A B AR experiment, a new D + s state is observed inthe inclusive DK mass distribution near 2.86 GeV /c in three independent channels. The decay to twopseudoscalar mesons implies a natural spin-parity forthis state: J P = 0 + , − , . . . . It has been suggestedthat this new state could be a radial excitation of D ∗ sJ (2317) [49] although other possibilities cannot beruled out. In the same mass distributions a broadenhancement around 2.69 GeV /c is also observed, itis not possible to associate it to any known reflectionor background. This analysis is published [50]. An-other B A B AR analysis[51], has searched for resonancesin B → D ( ∗ ) D ( ∗ ) K decays in 22 decay modes us-ing 347 fb − data sample recorded at the Υ (4 S ) res-onance. The D K and D ∗ K invariant mass distri-butions are built with 8 decay modes each. Both dis-tributions show a resonant enhancement around 2700MeV /c . However, due to an unknown structure atlow mass in the D K invariant mass distribution andto the possible additional resonances in the signal re-gion in the D ∗ K invariant mass distribution, a fullDalitz analysis in necessary and is ongoing in order toextract the D sJ (2700) + parameters.
4. Conclusion
Although the nature of the newly discovered charmresonances is not yet fully understood, the resonancesare interpreted as molecular or hybrid states in mosttheoretical papers. It will be interesting to see if theseinterpretations are confirmed by future measurementsand analyses.
References [1] C.W. Bauer, D. Pirjol, and I. W. Stewart, Phys.Rev. Lett. , 201806 (2001).[2] M. Bauer, B. Stech, M. Wirbel, Z. Phys. C ,103 (1987).[3] J. Botts and G. Sterman, Nucl. Phys. B325 , 62(1989).[4] H-n. Li and G. Sterman, Nucl. Phys.
B381 , 129(1992).[5] M. Beneke et al. , Nucl. Phys.
B591 , 313 (2000).[6] M. Neubert and B. Stech in
Heavy Flavors editedby A.J. Buras and M. Lindner, 2nd ed. (Worldscientific, Singapore, 1998).[7] C.W. Bauer, D. Pirjol, and I. W. Stewart, Phys.Rev. D , 054022 (2002).[8] Y.Y. Keum et al. , Phys. Rev. D , 094018(2004).[9] T. Kurimoto, Phys. Rev. D , 014027 (2006).[10] J.L. Rosner, Phys. Rev. D , 074029 (1999).[11] C. W. Chiang and J.L. Rosner, Phys. Rev. D ,074013 (2003).[12] B A B AR Collaboration, B. Aubert et al. , Phys.Rev. D , 032004 (2004).[13] Belle Collaboration, K. Abe et al. , Phys. Rev.Lett. , 052002 (2002) and S. Blyth et al. ,hep-ex/0607029, submitted to Phys. Rev. D .[14] T. Mannel et al. , Phys. Lett. B , 359 (1991). roceedings of the CHARM 2007 Workshop, Ithaca, NY, August 5-8, 2007 Figure 3: Fitted background-subtracted DK invariant mass distributions for (a) D K − π + K + , (b) D K − π + π K + , (c) D + K − π + π + K s , and (d) the sum of all modes in the 2.86 GeV /c mass region. The curves are the fitted functionsdescribed in the text. [15] M. Neubert, W. Rieckert, B. Stech, and Q. P.Xu, in Heavy Flavors edited by A.J. Buras andM. Lindner, (World scientific, Singapore, 1992).[16] S. Mantry, D. Pirjol, and I. W. Stewart, Phys.Rev. D , 114009 (2003).[17] F. Jugeau, A. Le Yaouanc, L. Oliver, and J.-CRaynal, Phys. Rev. D , 094010(2005).[18] B. Blok, and M. Shifman, Nucl. Phys. B389 , 534(1993).[19] M. Neubert, Phys. Lett. B , 173 (1998).[20] Charge-conjugate reactions are implied through-out.[21] S. Ahmed et al. , Phys. Rev.D , 031101(R) (2002) and M.S. Alam etal. , Phys. Rev. D , 43(1994).[22] Here D ∗∗ refers collectively to all the charmedmeson excited states with masses in the 2 . − . /c range.[23] B A B AR Collaboration, B. Aubert et al. , Phys.Rev. D , 111102(2006).[24] S. K. Choi et al. (Belle Collaboration), Phys. Rev.Lett. ,262001 (2003).[25] D. Acosta et al. (CDF II Collaboration), Phys.Rev. Lett. , 072001 (2004).[26] V. M. Abazov et al. (D0 Collaboration), Phys.Rev. Lett. , 162002 (2004).[27] B. Aubert et al. (BABAR Collaboration), Phys.Rev. D , 071103 (2005).[28] E. J. Eichten, K. Lane, and C. Quigg, Phys. Rev.Lett. , 162002 (2002); Phys. Rev. D , 094019(2004); T. Barnes and S. Godfrey, Phys. Rev.D , 054008 (2004).[29] F. E. Close and P. R. Page, Phys. Lett. B ,119 (2004).[30] K. K. Seth, Phys. Lett. B , 1 (2005).[31] E. S. Swanson, Phys. Lett. B , 189 (2004); N. A. Tornqvist, Phys. Lett. B , 209 (2004); M.B. Voloshin, Phys. Lett. B , 316 (2004).[32] W.-M. Yao et al. (Particle Data Group), J. Phys. G33 , 1(2006).[33] CLEO-c Collaboration, C. Cawlfield et al. ,Phys.Rev. Lett. , 092002(2007).[34] S. Godfrey and N.Isgur, Phys. Rev. D ,189(2005).[35] S. Godfrey and R. Kokoski, Phys. Rev. D ,1679(1991).[36] N.Isgur and M. B. Wise, Phys. Rev. Lett. ,1130(1991).[37] M. Di Pierro and E. Eichten, Phys. Rev. D ,114004(2001).[38] B. Aubert et al. (BABAR Collaboration), Phys.Rev. Lett. , 242001(2003).[39] D. Besson et al. (CLEO Collaboration), Phys.Rev. Lett. D68 , 032002(2003)[40] K. Abe et al. (BELLE Collaboration), Phys. Rev.Lett. , 012002(2004).[41] P. Krokovny et al. (BELLE Collaboration),Phys. Rev. Lett. , 262002(2003).[42] B. Aubert et al. (BABAR Collaboration), Phys.Rev. D , 031101(2004).[43] T. Barnes, F. E. Close and H. J. Lipkin, Phys.Rev. D , 054006(2003).[44] H. J. Lipkin, Phys. Lett. B , 50(2004).[45] B. Aubert et al. (BABAR Collaboration), Phys.Rev. D , 032007(2006).[46] B. Aubert et al. (BABAR Collaboration), Nucl.Instr. Meth. A , 1 (2002).[47] B. Aubert et al. (BABAR Collaboration), , Phys.Rev. D , 052006 (2005).[48] B. Aubert et al. (BABAR Collaboration),hep-ex/0607084.[49] E. van Beveren and G. Rupp, hep-ph/0606110. Proceedings of the CHARM 2007 Workshop, Ithaca, NY, August 5-8, 2007 [50] B. Aubert et al. (BABAR Collaboration), Phys.Rev. Lett. , 222001(2006).[51] B. Aubert et al.et al.