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Exploiting Di-Muon Production at PANDA

This study presents an overview of di-muon production at PANDA, focusing on the experimental apparatus, Drell-Yan process, and background rejection techniques. It covers topics like asymmetries, phase scans via J/ψ resonance, simulated yields, and energy choice methods. Details on the muon detector system and prototypes are discussed, along with the Drell-Yan asymmetries and interference studies. The study also delves into the characteristics of strong and electromagnetic decay amplitudes, alongside simulated yields for different processes. Overall, this research provides insights into the complex dynamics of di-muon production at PANDA.

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Exploiting Di-Muon Production at PANDA

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  1. Exploiting Di-Muon Production at PANDA Marco DestefanisUniversità degli Studi di Torino Stori’11 8th International Conference on Nuclear Physics at Storage Rings Frascati (Italy) October 9-14, 2011

  2. Overview • Experimental apparatus • Drell-Yan process and background • A. Bianconi Drell-Yan generator • Cut studies • Investigation of Drell-Yan asymmetries • Strong and electromagnetic relative phase via J/ψ resonance scan • Simulated yelds • Energy choice method • Summary

  3. The PANDA Detector STT Detectors Physics Performance Report for PANDA arXiv:0903.3905

  4. Muon Detector System Iarocci Tubes working in proportional mode Ar+CO2 gas mixture Prototype ready FE electronics in production JINR - Dubna TDR for the PANDA Muon System, 2nd Draft (May 2011) MDT cross section MDT layout

  5. Range System Prototype JINR - Dubna Muon Detector Layout

  6. Drell-Yan Process and Background • Drell-Yan: pp -> +-X cross section   1 nb @ s = 30 GeV2 • Background: pp -> +-X, 2+2-X,…… cross section   20-30 b m = 105 MeV/c2; m 145 MeV/c2 average primary pion pairs:  1.5 • Background studies: needed rejection factor of 107

  7. UNPOLARISED Drell-Yan Asymmetries Collins-Soper frame SINGLE-POLARISED . U = N(cos2φ>0) D = N(cos2φ<0) Asymmetry

  8. TMD: KT-dependent Parton Distributions Twist-2 PDFs Transversity Sivers Boer-Mulders

  9. CERN NA51 450 GeV/c Fermilab E866 800 GeV/c Di-Lepton Production pp-> l+l-X R.S. Towell et al., Phys. Rev. D 64, 052002 (2001) A. Baldit et al., Phys. Lett. 332-B, 244 (1994)

  10. Phase space for Drell-Yan processes x1,2 = mom fraction of parton1,2  = x1• x2 xF = x1 - x2  = const: hyperbolae xF = const: diagonal 1.5 GeV/c2 ≤ M ≤ 2.5 GeV/c2 PAX @HESR symmetric HESR collider 1

  11. A. Bianconi Drell-Yan Generator for pp • Antiproton beam • Polarized/Unpolarized beam and target • Drell-Yan cross section from experimental data • Selects event depending on the variables: • x1, x2, PT, , , S • from a flat distribution • Cross section: A. Bianconi, Monte Carlo Event Generator DY_AB4 for Drell-Yan Events with Dimuon Production in Antiproton and Negative Pion Collisions with Molecular Targets, internal note (PANDA collaboration) A. Bianconi, M. Radici, Phys. Rev.D71, 074014 (2005) & D72, 074013 (2005) A. Bianconi, Nucl.Instrum.Meth. A593: 562-571, 2008

  12. Next Step: Kinematic refit Background and Cuts • Sources of background • Primary background: Primary  & Secondary  from Primary  • Secondary background: Secondary  & Secondary  from Secondary  • Cuts and their effect on signal Rejection factor of 107

  13. 1 < qT < 2 GeV/c 2 < qT < 3 GeV/c DY Asymmetries @ Vertex SINGLE-POLARISED UNPOLARISED xP xP xP xP 500KEv included in asymmetries Acceptance corrections crucial! xP xP

  14. J/ψStrong and Electromagnetic Decay Amplitudes Strong → A3g Resonant contributions Фp(GMp )~ФγФ3g = 0 Фγ: relative A3g - Ap J/ψ→ NN Фp = 89°±15° [1,2] J/ψ→ VP (1-0-) Фp = 106°±10° [3] J/ψ→ PP (0-0-) Фp =89.6°±9.9° [4] J/ψ→ VV (1-1-) Фp = 138°±37° [4] NO INTERFERENCE! hadrons Electromagnetic → Aγ hadrons Non-resonant continuum affects the measured BR [5] affects Фp[5] INTERFERENCE WITH A3g! Non-resonant Continuum → AQED hadrons [1] R. Baldini, C. Bini, E. Luppi, Phys. Lett. B404, 362 (1997); R. Baldini et al., Phys. Lett. B444, 111 (1998) [2] J.M. Bian, J/ψ -> ppbar and J/ψ -> nnbar measurement by BESIII, approved draft [3] L. Kopke and N. Wermes, Phys. Rep. 174, 67 (1989); J. Jousset et al., Phys. Rev. D41,1389 (1990). [4] M. Suzuki et al., Phys. Rev. D60, 051501 (1999). [5] P. Wang, arXiv:hep-ph/0410028v2 and references therein.

  15. J/ψStrong and Electromagnetic Decay Amplitudes • IMAGINARY AMPLITUDES HARD TO BE EXPLAINED! • J/ψ perturbative regime (← ΓJ/ψ~ 93KeV ) • pQCD → real Aγ, A3g • QCD does not provide sizeable imaginary amplitudes (Фp 10° at most [1]) • a J/ψ - V glueball mixing [2] may explain imaginary amplitudes; and ψ’? • determination of phases Фp rely on theoretical hypotheses • EXPERIMENTAL DATA • no interference term in the inclusive J/ψ and ψ’ production • expected evidence of an interf. term in e+e-→ J/ψ→µ+µ- @ BESII [3] • no clear evidence of interf. or glueball in e+e-→ J/ψ→ ρπ @ BESII [4] [1] J. Bolz and P. Kroll, WU B 95-35. [2] S.J. Brodsky, G.P. Lepage, S.F. Tuan, Phys. Rev. Lett. 59, 621 (1987). [3] J.Z. Bai et al., Phys. Lett. D 355, 374-380 (1995). [4] J.Z. Bai et al., Phys. Rev. D 54, 1221 (1996).

  16. SimulatedYieldsfor e+e--> pp Δφ = 0° Δφ = 90° Δφ = 180° beam energy spread + radiative corrections continuum reference σ ~ 11 pb no corrections beam energy spread

  17. Simulated Yields for pp -> µ+µ- Δφ = 0° Δφ = 90° Δφ = 180° continuum reference σ ~ 18 pb no corrections beam energy spread

  18. Energy PointsChoice • What happens at 90° • Cross section simulated at 70°, 80°, 90°, 100°, 110° • Gradient Maximum interference: 0° • 2 points at low W • fit the continuum • Student test • slope • Deep position • Beginning of Breit-Wigner (σ90-σi)/σ90 i = 70 i = 80 i = 100 i = 110

  19. Summary • Interest on Drell-Yan studies • 1.5 < Mμμ < 2.5 GeV/c2 • Cuts for background rejection • Rejection factor achieved for secondary background: > 5 106 • Kinematically constrained refit still to be investigated • Few months of data taking are enough to: • evaluate unpolarised and single-spin asymmetries with good accuracy  investigate their dependence on qT,μμ • Interest on J/ψ decay amplitudes • Simulation of different phases • Reasonable energy point choice • Optimization of the procedure

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