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Understanding dd  4 He p 0 Experimental Studies at COSY

Understanding dd  4 He p 0 Experimental Studies at COSY. V. Hejny Institut für Kernphysik Forschungszentrum Jülich. Near threshold p -production in dd  3 A N p ANKE The future WASA-at-COSY setup p-wave contributions to dd  4 He p 0 WASA-at-COSY. p 0.

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Understanding dd  4 He p 0 Experimental Studies at COSY

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  1. Understanding dd  4He p0Experimental Studies at COSY V. HejnyInstitut für KernphysikForschungszentrum Jülich • Near threshold p-production in dd 3A N p ANKE • The future WASA-at-COSY setup • p-wave contributions to dd 4He p0 WASA-at-COSY

  2. p0 χPT a Prod. χPT χPT ? ISI dd  (A=3) N p d d I = 1 3P0 (at thr.) Charge Symmetry Breaking in dd 4Hep0 Theoretical analysis within ChPT • first results and status: see talks today ... • expectation: CSB hadronic matrix elements  10% precision Further experimental constraints and checks needed • e.m. CSB contributions e.g. from dd ap0g or ga ddp0 • test of ISI in a similar, CS conserving reaction • p-waves in dd ap0to be measured with WASA-at-COSY

  3. p N + 3A Prod. ISI 3P0 (at thr.) d d dd (A=3)Np • Isospin conserving, same initial state • no free parameters in calculation all fixed from NN  NNp • calculations up to N3LO: stot: 10% uncertainty + systematics from ISI • Additional aspects • 3H-p / 3He-p interaction with I=1 fixed • role of 4-body forces • Experimentally • lowest (isospin conserving) p-production channels in dd: dd  3H p p0, 3He n p0, 3He p p-, 3H n p+ no data available ! • theor. demand: Ds/s < 20 - 30% (at least)

  4. Proposal 139 Near Threshold p Production in dd  (3HeN) p and dd  (3HN) p V. Hejny1, A. Magiera2, M. Büscher1, D. Chiladze1,C. Hanhart1, A. Kacharava3, A. Khoukaz4, T. Mersmann4,M. Śmiechowicz2, H. Ströher1, A. Wrońska1,2 and the ANKE Collaboration1Institut für Kernphysik, Forschungszentrum Jülich, Germany2Institute of Physics, Jagiellonian University, Cracow, Poland3Physikalisches Institut II, Universität Erlangen-Nürnberg, Germany4Institut für Kernphysik, Universität Münster, Germany

  5. Cooler Synchrotron COSY at FZ Jülich • Proton and deuteron beams • pmax 3.65 GeV/c(Ep = 2.82 GeV, Ed = 2.2 GeV) • MProd 1.1 GeV/c2 (in pp) • cooling (stochastic, electron) • polarisation • Internal installations • thin, windowless gas targets / strip targets • polarized gas targets • External installations • extracted, high quality, focussed beams • compact LH2, LD2, ... targets

  6. The ANKE spectrometer • ANKE: internal magnetic spectrometer Beam

  7. dd (A=3)Np • dd  3Hpp0, 3Henp0, 3Hepp-at threshold • acceptance of ANKE well suited for this kinematics

  8. Hit Characteristics in ANKE

  9. dd (A=3)Np • dd  3Hpp0, 3Henp0, 3Hepp- at threshold • acceptance of ANKE well suited for this kinematics • March 2005: measurement at COSY/ANKE

  10. dd (A=3)Np • dd  3Hpp0, 3Henp0, 3Hepp- at threshold • acceptance of ANKE well suited for this kinematics • March 2005: measurement at COSY/ANKE • Goal: Ds/s < 20-30% • crucial: absolute beam momentum (phase space, i.e. s~ Q2 ?) luminosity

  11. Normalisation • Beam momentum • absolute value from COSY: Dp/p ≥ 10-3 • method: continuous ramp from 1.030 to 1.065 GeV/c (DQ = 8MeV) • full excitation functions, momentum calibration by crossing all reaction thresholds • Luminosity • no data for elastic dd scattering • instead: • quasi-elastic pp and pd scattering • exploit momentum shift by energy-loss in the target !- measured by frequency shift in COSY- successfully used in previous ANKE beam times- expected precision < 10 % • ramped beam + fixed beam momentum: p t

  12. stot = f(stot(pd  3Hep0)) p0 d 3He p n d Status • To get Ds/s < 20-30%: estimated using a non-relativistic model, spectator kinematics: 25000 3HeNp-events in 10days (Leff 6 · 1029 cm-2s-1,s  ...100 nb) • Data: first glance • 3He can be identified • event rates in agreement with estimation  at least statistics is fine ... 3He

  13. dd (A=3)Np • dd  3Hpp0, 3Henp0, 3Hepp- at threshold • acceptance of ANKE well suited for this kinematics • March 2005: measurement at COSY/ANKE • Goal: Ds/s < 20-30% • crucial: absolute beam momentum (s~ Q2) luminosity • Status • Online: • 3HeNp events identified, statistics within expected range • Offline: • energy, time, momentum calibration close to be finished • no (preliminary) results available yet

  14. shutdown of CELSIUSend of June 2005 WASA at COSY 1m The Future: WASA-at-COSY • WASA: • 4p detector for charged and neutral particles • operated at CELSIUS storage ring, TSL/Uppsala

  15. Some Features of WASA • Pellet target • internal, windowless target • H2/D2 pellets, ø = 30 mm • L  1032 cm-2s-1, beam life time  minutes Beam

  16. Beam Edep vs. Ekin Some Features of WASA • Multi-layer forward detector (enery loss, hit position) • q = 3°… 18°, tracker resolution 0.2° • stopping p,p,d,a up to 170, 300, 400, 900 MeV • energy resolution 3% (Tstopped) … 8% (2x Tstopped)

  17. Beam Some Features of WASA • Inner tracking (straw tube tracker) • superconducting solenoid (0.18·X0), 1.3 T • momentum res. (sp/p): 80° 2% (100-500 MeV/c) 35° 4%-6% 20° 6%-10%

  18. Beam Some Features of WASA • CsI(Na) electromagnetic calorimeter: • 16·X0, q = 20° … 170°, full azimuthal acc. • angular res.:  5° • energy res.: g @ 100 MeV 8% charged part. 3%

  19. Timeline • Jul.-Oct. 2005 Dismounting WASA at CELSIUS • Nov. 2005 Transfer to COSY • Aug. 2006 Assembly at COSY finished • Sep. 2006 Start commissioning • Jan. 2007 Begin of experimental program

  20. Physics: Primary objective • Studying fundamental symmetries to understand hadronic systems: • isospin symmetry / quark mass effects • h and h’ decays • dd → 4He p0 • C,P,T (violation) and combinations • h and h’ decays furtherTalks by M.Wolke: “h and h’ decays with WASA” V.Kleber: “a0-f0 mixing”

  21. The WASA at COSY Collaboration 137 Members 24 Institutes, 7 Countries Proposal “WASA-at-COSY” available as arXiv:nucl-ex/0411038 (b/w) or at http://www.fz-juelich.de/ikp/wasa (color)

  22. dd  4Heπ0 : Proposed studies Theoretical input • consistent analysis of Afb(npdπ0) and dd  4Heπ0 • result: parameter-free prediction of p-wave contributions in dd4Heπ0 Experimental program • on-set of p-waves in dd  4Heπ0(proposed: Q = 60 MeV) • contributions from Δ resonance at higher energies • energy dependance: helps to minimize systematics from dd ISI Extraction of p-waves: • problem: no interference of s and p (symmetric initial state)s-d and p-p interferences have same signature • only polarized deuteron beam allows mixed s-p term  measuring asymmetries / analyzing power / ds/dW disentangle s-, p- and d-waves

  23. π0 γγ in CsI calorimeter • q = 20° … 170°, full azimuthal acc. • angular resolution  5° • energy resolution (g @ 100 MeV): 8% • a in forward detector • q = 3° … 18°, tracker resolution 0.2° • stopping power: Ea 900 MeV • Dpa/pa 2-3% low QΔ resonance 350 MeV 250 MeV General concept Coincidence measurementof a and p0in WASA

  24. a identification: Experience at ANKE dd4Heη at ANKE • large proton background(nps)d  psX, pd and pN quasifree same rigidity as  ! • cut on energy loss very efficient • however:s(4Heη)  103·s(4Hep0) !

  25. θrec vs θmeas Trigger Hodoscope ΔEvs Etot a identification with WASA More favorable situation at WASA • pion detection: π0γγ  further constraints • additional plastic layers for proton rejection • break-up protons remain at  0º (no transverse magnetic field) • however: no momentum reconstruction θrec vs Etot

  26. Beam time estimates • Goal: extraction of CSB p-wave contributions • asymmetries, angular distributions  Nπ, tot ≥1000 (e.g. DN/N  10% per bin) • Luminosity • Polarized deuteron beam Nd = 5·109 ... 1·1010 in flat top • WASA pellet target deff 5·1015 cm-2 • Beam time • p-waves between threshold and Δ region • Q  60 MeV (pbeam 1.2 GeV/c) • σtot, estimated  75 pb  1 ... 3 weeks • p-wave contributions from Δ resonance • Q  160 MeV (pbeam 1.6 GeV/c) • σtot, estimated  120 pb  1 ... 3 weeks L  3·1031 ... 1·1032 cm-2s-1

  27. Some crucial points • Moderate resolution for p0 and a • no time-of-flight, no magnetic field in forward direction • combined analysis / kinematical constraints • Background • lower limit in Q defined by WASA beam pipe • break-up channels p0X open • break-up (beam-)protons (neutrons, beam halo ?) • additional detector elements necessary • Statistics • estimated: IUCF result scaled (s-wave) • sensitivity on p-wave component • what to measure: asymmetry / analyzing power / ds/dW ?

  28. Summary • Charge Symmetry Breaking • a tool to deepen our understanding of QCD symmetries • COSY allows selective experiments according to • isospin (protons, deuterons) • spin (polarized beams) • dd (A=3)Np at ANKE • providing data for dd initial state with similar kinematics • in addition: 3He-p / 3H-p at I=1, 3-body forces • WASA provides • detection of charged and neutral particles • pellet target for highest luminosities • WASA at COSY: a tool for decisive investigations on Charge Symmetry Breaking

  29. Thank you!

  30. WASA: Overview • WASA comprises • Pellet Target • resulting luminosities: L = 1032 cm-2s-1 • Central Detector • el.-mag. calorimeter • superconducting solenoid • mini drift chamber • plastic scintillator barrel • Forward Detector • trigger hodoscope • range hodoscope • drift chamber • at Cosy: Cerenkov detector

  31. • Identification of reaction channels: • tpp0 and 3Hepp- identified by coincidence with proton • 3Henp0unambigiously identified up to threshold  for higher momenta: s(3Henp0) = s(3HeNp) - s(3Hepp-) • however: extraction of tnp+ the same way is difficult

  32. Charge-Symmetry Breaking • Charge Symmetry:rotation in isospin space, 180º around I2-axis interchange of ud quarks • Approximate symmetry in QCD: • quark-mass differences, mu md • different electromagnetic corrections for u and d-quark • CSB is an experimental handle on these effects • Recent results: • Afb(np  dp0) (Opper et al., PRL 91, 212302) • dd ap0 at threshold (Stephenson et al., PRL 91, 14302) • cross section would vanish in a charge-symmetric world • direct measurement of CSB-amplitude squared • Task: extraction of CSB hadronic matrix elements

  33. X π N N π N X Exploiting CSB ChPT Effective Lagragian links various observables: • Nucleon mass splitting: mn - mp = ΔMstr + ΔMem = 1.26 MeV • ΔMstr,ΔMemnot known individually • ΔMem - (0.76  0.30) MeV (negative!) • additional contraints desirable • πN scattering length • a(π0p) - a(π0n) = f(ΔMstr) • however: no direct measurement of π0N large e.m. corrections in πN • instead: πN rescattering in pion production f(ΔMstr - 1/2 ΔMem)

  34. Here: dd  4He 0 Pion production in dd4Heπ0 • σ  0 in a charge symmetric world  σ  |MCSB|2 • complementary to npdπ0: • different strength of CSB terms • dd initial state more demanding • recent result: Stephenson et al.(PRL 91 (142302) 2003)stot (Q  1.4 MeV) = 12.7  2.2 pbstot (Q  3.0 MeV) = 15.1  3.1 pb consistent with s-wave Q  1.4 MeV Q  3.0 MeV International Workshop on Charge Symmetry Breaking June 13-17, 2005, ECT, Trento, Italy

  35. Production Rates of h’ In comparison: Dafne/KLOE 400000 h’ by mid 2005 similar statistics in ~ 4 days from WASA at COSY

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