R. W. Stanek

Design and construction of the ZEUS barrel calorimeter

Abstract We present the mechanical design and construction techniques used in building the barrel calorimeter for the ZEUS detector. The latter is currently under construction for use at the HERA electron-proton colliding beam facility. The calorimeter consists of 32 wedge shaped modules with approximate dimensions of 3×0.5×1.7 m 3 . The modules use alternate layers of depleted uranium and scintillator with one radiation length sampling. The light is collected via wavelength shifter plates placed on the sloping sides of the modules and read out by photomultiplier tubes located at the outer radius. The unit cell dimensions result in a ratio e h = 1 which yields an optimal energy resolution for hadronic jets. The placing of the structural components and the arrangement of the cracks between modules were chosen to maximize the uniformity of the response. Details of the construction and assembly effort needed to realize the total calorimeter are given. We finally describe the procedures used for transporting the completed modules to DESY and to install them on ZEUS.

Analyzing power in inclusive π+ and π− production at high xF with a 200 GeV polarized proton beam☆

The analyzing power in inclusive charged pion production has been measured using the 200 GeV Fermilab polarized proton beam. A striking dependence in x(F) is observed in which A(N) increases from 0 to 0.42 with increasing x(F) for the pi+ data and decreases from 0 to -0.38 with increasing x(F) for pi- data. The kinematic range covered is 0.2 less-than-or-equal-to x(F) less-than-or-equal-to 0.9 and 0.2 less-than-or-equal-to p(T) 2.0 GeV/c. In a simple model our data indicate that at large x(F) the transverse spin of the proton is correlated with that of its quark constituents.

A measurement of σtot (γp) at √s=210 GeV

Abstract The total photoproduction cross section is determined from a measurement of electroproduction with the ZEUS detector at HERA. The Q 2 values of the virtual photons are in the range 10 −7 Q 2 −2 GeV 2 . The γp total cross section in the γp centre of mass energy range 186–233 GeV is 154 ± 16 (stat.) ± 32 (syst.) μ b.

Measurement of elastic {gamma} photoproduction at HERA.

The photoproduction reaction gamma p ->mu+ mu- p has been studied in ep interactions using the ZEUS detector at HERA. The data sample corresponds to an integrated luminosity of 43.2 pb^{-1}. The Upsilon meson has been observed in photoproduction for the first time. The sum of the products of the elastic Upsilon(1S), Upsilon(2S), Upsilon(3S) photoproduction cross sections with their respective branching ratios is determined to be 13.3 +- 6.0(stat.)^{+2.7}_{-2.3}(syst.) pb at a mean photon-proton centre of mass energy of 120 GeV. The cross section is above the prediction of a perturbative QCD model.Abstract The photoproduction reaction γp→ μ + μ − p has been studied in ep interactions using the ZEUS detector at HERA. The data sample corresponds to an integrated luminosity of 43.2 pb −1 . The ϒ meson has been observed in photoproduction for the first time. The sum of the products of the elastic ϒ(1S),ϒ(2S),ϒ(3S) photoproduction cross sections with their respective branching ratios is determined to be 13.3±6.0(stat.)+2.7−2.3(syst.) pb at a mean photon-proton centre of mass energy of 120 GeV. The cross section is above the prediction of a perturbative QCD model.

Measurements of ΔσL (np) between 500 and 800 MeV

Abstract A measurement of Δσ L (np), the difference between neutron-proton total cross sections in pure longitudinal spin states, is described. Data were taken for five energies between 500 and 800 MeV, with statistical errors of ≈ 1.5 mb and an estimated normalization error of 6%. The data, combined with other results, show some evidence for an elastic I =0 spin-singlet resonance with mass ∼ 2213 MeV and width ∼ 74 MeV, or a coupled-triplet resonance with similar mass and width.

Measurement of single spin asymmetry in η-meson production in p↑p and p̄↑p interactions in the beam fragmentation region at 200 GeV/c

We present experimental results on measuring a single spin asymmetry in η-meson production in the interaction of transversely polarized protons and antiprotons at plab = 200 GeV/c with a proton target in the region 0.2 < xF < 0.7 for p↑p, 0.3 < xF < 0.7 for p↑p and 0.7 < pT < 2.0 GeV/c. A comparison of single spin asymmetries in π- and η-meson production is made.

MEASUREMENT OF GAS BREMSSTRAHLUNG FROM ELECTRON STORAGE RINGS

Abstract Bremsstrahlung is produced in electron storage rings when the particle beam interacts with the storage ring components or with the residual gas molecules in the storage ring vacuum. The interaction of the particle beam with the gas molecules occurs continuously during storage ring operation. At straight sections of a storage ring, the gas bremsstrahlung contribution from each interaction adds up to produce a narrow monodirectional photon beam that travels down the beamlines. At the Advanced Photon Source (APS), where the stored electron beam energy is 7 GeV, gas bremsstrahlung generated in the straight sections of the insertion device beamlines, which is a total of 15.38 m in effective length, can be significant. This paper presents the results of the bremsstrahlung spectrum and energy measurements from the insertion device beamlines of the APS using a hermetic lead glass calorimeter. The calorimeter consists of 25 lead glass blocks, each 6.3 cm × 6.3 cm × 35 cm, stacked into a 5 × 5 array. Phototubes connected to the lead glass blocks collected the signals. The calorimeter is calibrated using the maximum energy of the observed bremsstrahlung spectrum. The total energy radiated and the bremsstrahlung spectrum were measured as a function of the storage ring beam current for both electrons and positrons of 7 GeV energy. Vacuum in the straight section was continuously monitored, and measurements to determine the nature of the residual gas inside the storage ring were performed. The measured bremsstrahlung spectra are fitted to a function that shows an approximate 1 E behavior. The gas bremsstrahlung rate from the APS undulator beamline straight path of 15.38 m is measured as 60.0 ± 2.0 GeV/s/nT/mA. Significant contribution of bremsstrahlung from sources other than the residual gas molecules is observed. The maximum bremsstrahlung energy measured in a beamline during the experiment is 369.0 ± 22.0 GeV/s/nT/mA.

New optical technology for low mass intelligent trigger and readout

New optical devices offer the potential for reductions in mass, power, and cost of data paths for on-board trigger and readout of tracking detectors. We give examples of optical modulators, MEMS beam steering devices, and optical coupling. We also present results on radiation hardness of materials as well as different approaches to using optics in triggering.

Measurement of KLL and KNN in pd → npp at 500, 650 and 800 MeV

Abstract Measurements of the spin transfer parameters, KNN and KLL, at 500, 650 and 800 MeV are presented for the reaction p d → n pp at 0°. The data are useful input to the NN data base and indicate that the quasi-free charge exchange (CEX) reaction us a useful mechanism for producing neutrons with at least 40% polarization at energies as low as 500 MeV.

Modulator based high bandwidth optical readout for HEP detectors

Optical links will be an integral part of future LHC experiments at various scales from coupled sensors to off-detector communication. We are investigating CW lasers and light modulators as an alternative to VCSELs. Light modulators are small, use less power, have high bandwidth, are reliable, have low bit error rates and are very rad-hard. We present the quality of the links at 10Gbps and the results of radiation hardness measurements for the modulators built based on LiNbO3, InP, and Si. Also we present results on modulator-based free space data links, steered by MEMS mirrors and optical feedback paths for the control loop.