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Preparation of new polarization experiment SPASCHARM at IHEP

Preparation of new polarization experiment SPASCHARM at IHEP. V.V. Abramov on behalf of the SPASCHARM collaboration Institute for High Energy Physics, Protvino, Russia. Outline. Introduction Physical motivation The first stage of SPASCHARM experiment Beams and targets

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Preparation of new polarization experiment SPASCHARM at IHEP

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  1. Preparation of new polarization experiment SPASCHARM at IHEP V.V. Abramov on behalf of the SPASCHARM collaboration Institute for High Energy Physics, Protvino, Russia

  2. Outline Introduction Physical motivation The first stage of SPASCHARM experiment Beams and targets Experimental setup Expected accuracy and mass plots (MC simulation) Status of the project Summary

  3. Introduction Numerous experiments measured significant spin effects in exclusive andinclusive reactions for hh, hA, AA & lN-interactions. A lot of models have been proposed to explain the data. None of them is able to describe the full sample of the data. The single-spin effects are very large at moderate pT and large xF mostly. The energy dependence of single-spin observables is, as a rule, rather weak. Possible non-pertubative nature of large spin effects requires high statistics and high accuracy measurements of large variety of processes in order to reveal general regularities and to build later an adequate model or mechanism.

  4. SPASCHARM as a next step after PROZA completion A new experiment SPASCHARM is continuation of PROZA experiment at IHEP and is devoted to systematic study of polarization phenomena in hadron-hadron interactions in the energy range 10-70 GeV in lab. frame. In PROZA experiment were detected only particles decaying into gamma’s in the final state. In SPASCHARM we will measure both neutral and charge secondary particles.

  5. Physical motivation Usually the main motivation for polarization studies declares the task of studying the spin structure of the proton. However, as shows theoretical analysis of the results, the most valuable information is related to the dynamics of the strong interaction of hadrons and quarks in the area of confinement. Spin effects can be linked to such fundamental problems as spontaneous chiral symmetry breaking, the appearance of mass for quarks and hadrons, the formation in hadrons quasi-particles - constituent quarks and the quark confinement. For discrimination of different theoretical approaches are needed systematic studiesof single-spin asymmetry and polarization in a large number of exclusive and inclusive processes. Such a program can be performed on the proposed setup SPASCHARM.

  6. The first stage of SPASCHARM experiment The program for the first phase of polarization studies in SPASCHARM experiment is devoted tothe measurements ofsingle-spin asymmetry (AN) on the polarized target in the exclusive and inclusive production of light particles.In addition, thehyperon and vector meson polarization is going to be studied for different beams and targets. A possible and very interesting option is a creation of polarized proton beam using decays of Lambda hyperons, produced in the internal IHEP accelerator target (Prof. S.Nurushev’s idea). The use of light ion beams (d, C12) is another option, which is under study. Single spin effects for ion beam could be large due to superposition of color fields of many projectile quarks. All the above could be combined with spin transfer studies.

  7. Observables The measured observables are: the analyzing power AN, which can be measured with high accuracy due to full azimuthal setup coverage; the hyperon transverse polarization PN, which can be measured using angular distributions of the hyperon decay products in its rest frame; the density matrix element ρ00, which can be measured for 2-boson decays of vector mesons; another observable α = (σT – 2σL)/(σT + 2σL)can be measured for vector meson decay into fermion-antifermion pair. The SPASCHARM setup will measure charged particle multiplicity as an additional variable, which could be related with the intensity of color field in the interaction volume.

  8. Detected particles The SPASCHARM setup will detect directly charged particles, such as π±, K±, p, p̃, e±, μ± and neutral particles, such as K0L, n, γ. A lot of resonances, charged and neutral, can be detected via their decay products, listed above: π0, η, η´, K0S, K*±(892), K*0(892), ω(782), ρ±(892), ρ0(892), φ(1020), Δ++(1232), Δ̃--(1232). Hyperons and corresponding antihyperons: Λ, Ξ-,0, Σ0. The above variety of detected particles, combined with different beam options, allow us to study in a systematic way tens of reactions, inclusive and exclusive.

  9. Examples of exclusive data Asymmetry in the reaction of -р ω(782)n at an energy of 40 GeV [PROZA], where ω(782)-meson decays into 0and. During 90 days at SPASCHARMand using two decay modes - into+-0and0the statistics could beincreased by a factorof 20, up to 600000 events. I.А. Avvakumovet al., Yad.Fiz.42 (1985)1146.

  10. Example of inclusive data Au + Au → Λ↑ + X BNL: √s =4.86 GeV, R.Bellwied for E896 Collaboration, Nucl.Phys. A698(2002)499. The polarization of Λ-hyperon in the reaction Au + Au → Λ + X at the energy √ s = 4.86 GeV. Curve - effective color field model prediction. V.V.Abramov, Phys. of Atom. Nucl. 72(2009)1872.

  11. Example of inclusive data p↑ + p → π0 + X Analyzing power AN for E704, STAR and PROZA data. Line – linear fit for xA> 0.2. Scaling variable: xA = (xR + xF)/2, where xR = p/pmax and xF = pZ/pmax in c.m. frame.

  12. Beams In the first phase of the polarization studies we plan to use a secondary negative meson (mostly pion) beam and primary proton beam in energy range 10 – 34 GeV and 50-60 GeV respectively. The intensity of the above beams will be up to 3·106/spill with 0.5-1.5 sec duration. The extraction of positive pion beam is under study. The particle composition of thenegative beam (π-/K-/p): 97.9/1.8/0.3%, measured using beam Cherenkov counters,will allow us to study beam flavor dependence for some most intense reactions. Electron beam in energy range 1-34 GeV is available for a calorimeter calibration. Possible polarized proton beam from decays of Lambda hyperons, produced in the internal IHEP accelerator target, can have up to 40% transverse polarization and intensity up to 106/spill.

  13. Polarized Target In the first phase of the polarization studies we plan to use polarized frozen propan-diol target, which is currently upgraded by our JINR (Dubna) colleagues. The main parameters of polarized target: chemical composition - C3H8O2, length - 20 cm, diameter - 2 cm, the proton polarization up to90%, the dilution factor is about 10. The amount of material in the target corresponds to 15.2% of interaction length for 60 GeV protons and to 10% for 34 GeV π- - mesons.

  14. The Polarized Target The polarized target during upgrade out of the target magnet.

  15. Experimental setup SPASCHARM 100 cm. Schematic view of SPASCHARM setup. Plan view.

  16. Experimental setup SPASCHARM The setup is a spectrometer for registration of charged particles, neutrons, K0L-mesons and photons in the forward and central regions. The apparatus has an aperture of 2π in the azimuthal angleφ, which allows to minimize systematic errors for different observables. Chambers inside the magnet have acceptance 420x310 mrad2. The setup contains polarized proton target, tracking system withmomentum resolution 0.4% at 10 GeV/c, spectrometer magnet (1.5 T·m), system of identification of secondary particles (multi-channel Cherenkov counters and hopefully TOF), electromagnetic and hadron calorimeters and muon detector. There are also a charged particle multiplicity detector, which is also planned to be used as a time-of-flight system,the target guard system and the trigger counters.

  17. Electromagnetic lead glass calorimeter The lead glass ECAL will have 960 channels (24x40 matrix). The energy resolution is (812)%/Е. Module size is 38*38*450 мм3. The peripheral part of ECAL consists of sandwich type modules, 1280 channels in 80 supermodules. Each layer has 2.5 mm Pb and 5 mm scintillator plates. Cell size is38*38 мм2. Assembling of the lead glass ECAL-720.

  18. Multi-channel Cherenkov counters The Cherenkov counter #1 is 1.5m long, uses freon-22 as the radiator and has 8 channels (Russian PMT FEU-174). It detects pions above 3 GeV/c and kaons above 11 GeV/c. The Cherenkov counter #2 is 3m long, uses air as the radiator and has 16 channels. It detects pions above 6 GeV/c and kaons above 23 GeV/c. #2 #1 The view of multi-channel counters #1 and #2.

  19. Multi-channel Cherenkov counters The amplitude distribution in channel 5 ADC of counter #1 for 28 GeV pion beam. One photo-electron peak is seen. The distribution of the total number of photoelectrons in counter #2 for 28 GeV pion beam. Amplitutes for all 16 channels are summed.

  20. The target magnet and the guard system The target guard system should detect charged particles and gammas at large polar angles (14o < θ < 166o) in laboratory frame. The device works in magnetic fieldof 0.45 T and has 4 channels for charged particles and 2 channels for gammas, with corresponding segmentation in angle φ. The polarized target magnet and the target guard system are constructed and will be tested in 2010.

  21. The GEM detectors Two GEM detectors are located downstream the target. Their purpose - a precise measurement of track parameters. The GEMs also will be used for the registration of resonances and hyperons. The width of the strip is 0.4 mm, transverse size will be 30x30 cm2. The beam GEMs size will be 10x10 cm2. Test of the GEM prototype detector 10x10 cm2.

  22. Examples of mass plots (MC) for 34 GeV pion beam Effective mass distributions for π−p→h +x: h=π0→γγ (a); h=η→γγ (b); h=K0S→ π+π− (c); h=ρ0(770)→ π+π− (d), for 6·107interactions. (c) (a) (b) (d)

  23. Examples of mass plots (MC) for 34 GeV pion beam Distributions for π−p→h +x: h=K0*(892)→ K+ π− (a); h= K̃0*(892)→ K– π+ (b); h=K+*(892)→ K+ π0 (c); h= K̃–*(892)→ K– π0 (d). (c) (a) (a) (b) (d)

  24. Expected number of events Nev for 6·1010π-p interactions

  25. Examples of mass plots (MC) for 60 GeV proton beam Distributions for pp→h +x: h=Λ→ p π− (а); h=Λ→ n π0 (b); h=Δ++→ p π+ (c); h=Ξ−→ Λπ− (d). (a) (c) (d) (b)

  26. Expected number of events Nev for 6·1010pp interactions

  27. SPASCHARM status and plans • Technical design (schematic) - 2010, • final (including detectors) – 2011. • Polarized target – 2010. • Veto (guard) system – 2010. • Multi-channel Cherenkov counters – 2010, • (possible modification - 2011). • New beam detectors (including fiber and GEM) -2012. • Tracking system • Prototype - 2010, • First 2 station of drift tubes - 2011, • Full tracking system (including GEM stations) – 2013.

  28. SPASCHARM status and plans • Spectrometer magnet – 2011. • Hadron calorimeter – 2012. • EMC (ECAL): - Existing calorimeter (EMC-720) – ready - New calorimeter (2240 channels) – 2013. • Muon detector – 2013. • Multiplicity hodoscopes – 2013.

  29. SPASCHARM status and plans • Electronics: - prototypes – 2010, - first production – 2011, - all electronics will be produced – 2013. • Data tacking - first test data tacking (only neutrals detected) – 2010, - first test data taking with charge particle registration – 2011, - data taking with full setup – 2013.

  30. Summary We propose a new experiment SPASCHARM, devoted to systematic study of polarization phenomena in hadron-hadron interactions in the energy range 10-70 GeV. We will continue the study of exclusive and inclusive reactions (which began at PROZA) in collisions of different hadron beamswith the transversely polarized target. A special feature of the project is the simultaneous measurement of several spin-dependent physical observables (the single-asymmetry, the polarization of hyperons, the spin density matrix elements for vector mesons, the parameters of spin transfer). The measurement of the charged hadron multiplicity in an event opens up new possibilities for investigating the nature of polarization phenomena.

  31. Summary Registration of charged and neutral particles in the final state in a large solid angle of the experimental setup in interactions of different beamswill alow us to explore dozens of different reactions, including a comparison of the effects of the interactions of the particles andantiparticles. Tracking system allows precision (0.4% at 10 GeV/c) measuring the momentum of charged particles, which is critical for the separation of resonances from combinatorial background. The SPASCHARM setup will allow to measure polarization effects with record high accuracy, especially if polarized beam is successfullyimplemented. Interesting spin physics is expected in a few years! Thank You!

  32. The SPASCHARM Collaboration V.V.Abramov, N.I. Belikov, A.A. Borisov,Yu.M. Goncharenko, V.N. Grishin, A.M. Davidenko, A.A.Derevshchikov, R.M. Fahrutdinov, Yu.D. Karpekov, Yu.V. Kharlov, V.A. Kachanov, D.A. Konstantinov, V.A. Kormilitsyn, Yu.M. Melnik, A.P. Meshchanin, N.G. Minaev, V.V. Mochalov, D.A. Morozov, L.V. Nogach, S.B. Nurushev, V.S.Petrov, A.V. Ryazantsev, P.A.Semenov, V.A. Senko, N.A. Shalanda, L.F. Soloviev, A.F. Prudkoglyad, A.V. Uzunian, A.N. Vasiliev, V.I.Yakimchuk, A.E. Yakutin, IHEP, Protvino, Russia N.A. Bazhanov, N.S. Borisov, V.G. Kolomiets, A.B. Lazarev, A.B. Neganov, Yu.A. Plis, O.N. Shchevelev, Yu.A. Usov JINR, Dubna, Russia V.A. Chetvertkova, SkobeltsynINP MSU, Moscow, Russia M.A. Chetvertkov MSU, Moscow, Russia A.A. Belyaev, A.A. Lukhanin, KhPTI, Kharkov, Ukraine

  33. Abstract A new experiment SPASCHARM devoted to systematic study of polarization phenomena in hadron-hadron interactions in the energy range 10-70 GeV is under preparation at IHEP (Protvino). The physical observables will be single-spin asymmetries, hyperon polarizations and spin-density matrix elements. An universal setup will detect and identify various neutral and charge particles in full azimuthal angle and wide polar angle by using polarized target. The SPASCHARM sub-detectors are being designed and constructed now. A possibility of obtaining a polarized proton beam for the SPASCHARM experiment from Lambda decays is under study.

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