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Charmonium, open charm and beauty production at HERA-B

Charmonium, open charm and beauty production at HERA-B. P IETRO F ACCIOLI , for the HERA-B Collaboration Università di Bologna and INFN. June 14, 2006 Asilomar Conference Grounds, Pacific Grove, California. outline. HERA-B detector and physics topics

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Charmonium, open charm and beauty production at HERA-B

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  1. Charmonium, open charm and beauty production at HERA-B PIETROFACCIOLI, for the HERA-B Collaboration Università di Bologna and INFN June 14, 2006 Asilomar Conference Grounds, Pacific Grove, California

  2. outline • HERA-B detector and physics topics • results and comparison with previous experiments highest energy among fixed-target experiments first data atnegative xF • J/ψ production • pT and xF distributions, A-dependence often unclear experimental picture, especially for p-A collisions • new: decay angular distributions observation of low-pT/|xF| effects • heavier states and feeddown to J/ψ • ψ′/ψ and kinematics • fraction of J/ψ’s from χc largest χcstatistics analyzed in hadron collisions test production models (pQCD + initial/final state interactions in nuclei) • fraction of J/ψ’s from b decays • charm • inclusive D0, D+, D*+ and ratios • A-dependence

  3. the HERA-B detector (top view) high resolution large acceptance (15-220 mrad) Tracking Vertex Detector 920 GeV/c protons electrons target wires (C, Ti, W) Magnet RICH MUON fixed nuclear target 20 m 10 m 0 m ECAL √s = 41.6 GeV A = 12 ÷ 184 good PID (e±, μ±, π, K, p) + photon reconstruction

  4. 800 104 102 600 10 400 103 entries (a.u.) 1 200 102 10-1 0 2.5 3.0 3.5 4.0 4.5 6 7 8 9 10 11 12 0.4 0.6 0.8 1.0 1.2 mμμ[GeV/c2] mee[GeV/c2] mμμ[GeV/c2] 107 ~50k KK 4000 MinBias data, run 20478 105 HP trigger, run 20595 3000 103 Ed3σ/dp3 [a.u.] entries (a.u.) 10 2000 10-1 pC γX 1000 10-3 0 0 1 2 3 4 5 6 7 8 1 1.02 1.04 1.06 1.08 mKK[GeV/c2] ET[GeV] physics at HERA-B dilepton trigger:~ 150·106 events • J/ψ, χc, ψ′, with A-dependence • Doμ+μ-(FCNC) • inclusive b production • , , ρ/ω  J/ψ (1S) ρ/ω (2-3S) ψ′ μ+μ- e+e- μ+μ- two independent channels(e+e- + μ+μ-) ‘hard photon’ trigger:~ 35·106 events ~ 210·106 minimum bias events • Ks,K*,Λ,,Ξ+- • pentaquarks • Do,D+,D*+,Ds • J/ψ direct γ,πo, η production with four different nuclei

  5. J/ψ and ψ′ signals full dilepton data sample (3 target materials) μ+μ- e+e- ~ 120000 J/ψ ~ 2200 ψ′ σJ/ψ ~ 64 MeV ~ 170000 J/ψ ~ 3000 ψ′ σJ/ψ ~ 44 MeV 104 104 J/ψ entries/(30 MeV/c2) entries/(25 MeV/c2) J/ψ 103 103 ψ′ ψ′ 2.5 3.0 3.5 4.0 2.8 3.2 3.6 4.0 m(e+e-)[GeV/c2] m(μ+μ-)[GeV/c2]

  6. W <pT>[GeV/c] Au A Ti 197 184 48 28 12 9 increase of <pT> with A C E789 (Au) Si Be A W Ti E771 (Si) HERA-B E672/E706 (Be) [a. u.] C pT[GeV/c] J/ψ production kinematics: pT distribution preliminary data (di-electron channel). Compatible results from the di-muon data, not shown here. comparison with p-A results at similar energy (√s = 38.8 GeV)

  7. E771 (Si) E672/706 (Be) E789 (Au) HERA-B(C) C E789 (Be, Cu) Ti W xF distribution Preliminary data (e+e-), compared with p-A results at 38.8 GeV first data centred at negativexF

  8. 1.0 0.9 0.8 0.7 -0.4 -0.3 -0.2 -0.1 0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 1.0 0.9 0.8 0.7 -0.4 -0.3 -0.2 -0.1 0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 A-dependence a Models (with variants): • - R. Vogt, PRC 61 (2000) 035203, NP A700 (2002) 539 • K.G. Boreskov & A.B. Kaidalov, JETPL 77 (2003) 599 B&K Vogt: final state absorption HERA-B preliminary (di-muon channel, carbon+tungsten double-wire runs) errors statistical only E866 38.8 GeV Be/Fe/W E789 38.8 GeV Be/C/Cu/W E772 38.8 GeV H2/C/Ca/Fe/W NA50 29.1 GeV Be/Al/Cu/Ag/W NA3 22.9 GeV H2/Pt xF

  9. direction of e+(μ+) as seen in the J/ψ rest frame θ polarization axis decay angular distribution: polarization frames Il Nuovo Cimento Vol. XXXIII, N. 2 (1964) Phys. Rev. D16, 2219 (1977) Collins-Soper (“CS”) 1) Gottfried-Jackson (“GJ”) bisector between beam and (–)target directions in the J/ψ rest frame target direction in the J/ψ rest frame = (-)J/ψdirection in the lab frame E866, NA3, etc. reformulated as “BEAM” 2) 3) helicity “HCM” beam direction in the J/ψ rest frame J/ψ directionin the hadron (p-n) CM frame CDF, NA60, etc. E615, E672-706, E771, E537, etc.

  10. (x axis reaction plane) parametrization example: example:

  11. lφ~  CS lφ BEAM HB 41.6 GeV p-C/Ti/W NA3 22.9 GeV p-Pt/p-H2 E615 21.8 GeV π±-W p-W/πW E537 15.4 GeV p-Be/πBe p-Cu/πCu / / / / HCM

  12. meaning of lθφ polar axis production plane lθφ ≠ 0means that the axes of the current frame are not principal axes of symmetry for the angular distribution. But it is always possible to define a reference frame with this property: the angular distribution can always be diagonalized to a form with lθφ = 0 The “natural” polarization frame has lθφ equal to zero: in such frame the decay distribution is symmetric and is described by only two parameters.

  13. lθφ <pT> [GeV/c] <xF> lθφ in the three frames preliminary, BEAM CS HCM (statistically ~100% correlated) • The three frames actually see the decay kinematics from different perspectives • CS the best frame?

  14. dN 1 N d(cosθ) cosθ cosθ preliminary <pT> [GeV/c] <xF> lθ and the hierarchy of frames preliminary dN/d(cosθ)  1 + λθcos2θ HCM (arb. norm.) BEAM (arb. norm.) CS HCM BEAM CS lθ |lθ| > |lθ| > |lθ|

  15. <pT> [GeV/c] <xF> <pT> [GeV/c] interpretation case 1 lθ HCM CS points = data, lines = Toy MC polarization generated in the CS frame … and translated into the HCM frame The data are consistent (for example) with a polarization generated in theCS frame lθ case 2 No hypothesis of generation in the HCM fr. can reproduce the data in the CS fr. generation in the HCM frame The CS frame is the best approximation of the “natural” polarization frame  physics: origin of J/ψ polarization CS

  16. E866 38.8 GeV p-Cu E444 20.6 GeV π±-C/Cu/W NA3 22.9 GeV p-H2 NA3 22.9 GeV p-Pt HB 41.6 GeV p-C/Ti/W experimental situation: CS frame J/ψ significantly polarized at low momentum (low pTand |xF|) lθ

  17. WA11 16.8 GeV π-Be 31.1 GeV π-Be 31.6 GeV p-Be 38.8 GeV p-Be E771 38.8 GeV p-Si E615 21.8 GeV π±-W HB 41.6 GeV p-C/Ti/W E672 /706 p-W/πW / p-Be/πBe / p-Cu/πCu / E537 15.4 GeV BEAM frame lθ

  18. E444 20.6 GeV π±-C/Cu/W CDF 1800 GeV p-p Run II WA92 25.7 GeV π±-W/Cu/Si NA60 17.3A GeV In-In HB 41.6 GeV p-C/Ti/W HCM frame polarization almost completely smeared out, except for pTvery close to zero lθ

  19. E705 NA38, NA50 & NA51 E288 NA38 E789 HERA-B E771 E444 HERA-B HERA-B 197 12 184 48 9 27 6 B′σ(ψ′)/Bσ(J/ψ) (%) 2 9 64 28 12 1 108 184 184 12 238 p-A 12 E331 ψ′-to-J/ψ production ratio Analysis finished. Combined results (e+e- + μ+μ-): • p-A results consistent within a 4% variation: • no apparent dependence on production energy and kinematics (different xF/y, cosθ windows) • slight dependence on the target nucleus: NA38/50/51 (+ E866)

  20. xF B′σ(ψ′)/Bσ(J/ψ) cosθ pT[GeV/c] ψ′ kinematics measured relative to the J/ψ distributions: B′σ(ψ′)/Bσ(J/ψ) as a function of xF. pT , cosθ HERA-B (full stat, e+e-/μ+μ- avg.) E789 (38.8 GeV) E771(38.8 GeV) NA50 (29.1 GeV) B′σ(ψ′)/Bσ(J/ψ)

  21. background: mixed events after background subtraction entries/(10 MeV/c2) m(μ+μ-γ)-m(μ+μ-) [GeV/c2] χc production selection: preliminary 2002/2003 data (di-muon sample) • measurement: • fraction of J/ψ’s from χc: • kinematical distributions • A-dependence from the 2000 data, with 370 ± 74 χc’s(μ+μ- + e+e-): R(c) = 0.32 ± 0.06 ± 0.04 [Phys. Lett. B 561, 61 (2003)] new data: 40bigger χcstatistics (the largest analyzed in a hadronic experiment)

  22. E771 (p-Si) E369/ 610/ 673 (p-Be) π-A ISR (p-p) 2000 expected final precision 2002/3 prelim. E705 (p-Li) CDF (p-p) HERA-B R(χc) preliminary evaluation (2002/2003 data): based on 1300 χc’s reconstructed in the di-muon channel (less than 10% of the total statistics) (21 ± 5)% of the produced J/ψ’s come from χc decays

  23. 46.2 ± 8.2 36.9 ± 8.1 σ(bb) (nb/nucleon) HERA-B 102 N. Kidonakis et al. E789 E771 10 σ(bb) = 14.9 ± 2.2stat±2.4syst nb/nucleon [Phys. Rev. D 73, 052005] 1 R. Bonciani et al. 1000 900 400 500 600 700 800 proton energy (GeV) J/ψ’s from b decays detached J/ψ’s pAbb X bJ/ψY e+e-/+-Y mee m - extrapolation to full xF range - normalization by total J/ψ cross sect. - correction by BR of b J/ψ

  24. χc ψ′ b J/ψ J/ψ J/ψ indirect and direct J/ψ production Using partial/preliminary HERA-B results: (7.0±0.4)% (21 ± 5)% (0.065±0.011)% (to be improved!) ISR extracted from MB data E705 E331 E444 UA6 (72 ± 5)% of the J/ψ’s are produced directly E331 NA3 p-p p-A E595 E288 curve: NLO NRQCD fit of all data (Maltoni et al., hep-ph/0601203) E672/706 E771 NA50 E789 NA3

  25. D0+D0 entries/(10 MeV/c2) entries/(10 MeV/c2) Kππ inv. mass [GeV/c2] Kπ inv. mass [GeV/c2] open charm: reconstructed signals 49 ± 10 preliminary D± D*± 194 ± 20 92 ± 11 preliminary preliminary entries/(0.5 MeV/c2) m(Kππ)-m(Kπ) [GeV/c2]

  26. D± HERA-B prel. D0+D0 HERA-B prel. without E789: with E789: √ √ D*± √ HERA-B prel. D cross sections comparison with p-p/p-A results • D0: unclear situation at high √s • E789 result clearly disfavoured • energy dependence well described in each case by the function • reflecting the behaviour of proton PDFs (Lourenço & Wöhri)

  27. √ √ D*±/D0 D±/D0 HERA-B prel. HERA-B prel. ud ud cross section ratios: experiments vs. isospin symmetry 3 polar. states ud PDG averages for D*0, D*± D0, D± feeddown BRs isospin symmetry violated by a factor of 1.87 ± 0.25 experiments

  28. W Ti (prel. D-meson average) curves: σpA = σpN·Aα C A-dependence mass spectra by target material (e.g. for D0): C Ti W 70 ± 11 19 ± 6 103 ± 14 entries/(10 MeV/c2) α(D0)= 0.92±0.08 α(D±)= 1.02±0.09 α(D*±)= 1.05±0.14 Kπ inv. mass (GeV/c2) experimental situation (p-A): αAVG.(xF~0) =1.01 ± 0.03 consistent with no suppression

  29. summary J/ψproduction in p-A collisions at √s = 41.6 GeV … • high statistics, clean signals, two decay channels • wide kinematical coverage • pT up to 5.5 GeV/c • negative xF • A-dependence: • flat suppression • down to xF ~ -0.35 300000 J/ψ’s … and its components: 5000ψ′’s • ψ′-to-J/ψ ratio • fraction of J/ψ’s fromχc • fraction of J/ψ’s from b 15000 χc’s 80 J/ψ’s from b J/ψ decay angular distributions • longitudinal polarization rapidly increasing in magnitude with decreasing pT and |xF| • strong hierarchy of frames: the direction of the original interaction (CS frame) is better than the J/ψ “flight” direction (HCM) as a reference for the observation of the “true” decay distribution open charm • D0, D±, D*± inclusive production cross sections and ratios • A-dependence consistent with α = 1

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