Beauty and Charm Production at Fixed-Target Experiments September 5-11, 2003 ISMD 2003 Erik Gottschalk Fermilab

Overview ISMD 2003 Erik Gottschalk Fixed-target experiments provide opportunities to study beauty and charm production for a wide range of beam particles and energies using many different target materials. studies of perturbative QCD and non-perturbative effects measurements necessary to understand heavy-ion experiments essential information needed for the design of new experiments Recent results: (new results since last year)  (bb) production cross section measurement production of doubly-charmed baryons asymmetry measurements (comparing particle/anti-particle production) kinematic correlations in heavy-quark production Not covered: A-dependence of heavy quark production charm production with neutrinos J/  production polarization

“Current” Fixed-Target Experiments with Recent Publications ISMD 2003 Erik Gottschalk

beauty production HERA-B – bb production cross section – Eur.Phys.J.C26: (2002) – preview of new results ISMD 2003 Erik Gottschalk

HERA-B Magnet RICH Vertex Wire Target p 920 GeV High p T Chambers Tracking Chambers (Inner+Outer) ECAL MUON 920 GeV protons from HERA Nuclear targets (wires) in beam halo Di-lepton ( , ee) trigger Data: run 2000: 8k J/  ’s run 2002/3: 300k J/  ’s, 200M m.b. events Physics topics: -  (b) - Charmonium production & suppression in nuclear matter - Min. bias physics

J/  Sample From 2002/3 Run dN/dx F (J/   e + e - ) M(  +  - ) M(e + e - ) Total: 300,000 J/  in both channels: -0.3 < x F < 0.1, 0 < p T < 5 GeV uncorrected

The HERA-B  (bb) Measurement b  J/  X   +  - X b  J/  X  e + e - X l + J/  B zz X l - IWIW 2) Identifyvia detached J/  vertices. upstream | downstream 3) Normalize to  (J/  ) (combine E789, E771, use  from E866: 356 nb/nucleon.) 1) Trigger on J/  (Plots from Run 2000)

b Signal,  (b) e+e-e+e- +-+-  TOT (bb) = nb/nucleon EPJ C26: 345, 2003 (after impact parameter, detached vtx cuts) Run 2000 result40% of Run 2002/3 data much improved  estimate soon (based on  11 detached J/  )

ISMD 2003 Erik Gottschalk charm production E835 –  c (1 1 S 0 ) resonance parameters - PLB 566 (2003) 45 E835 – interference study of the  c0 (1 3 P 0 ) (unpublished: hep-ex/ ) HERA-B – J/  production via  c decays – PLB 561 (2003) 61 E866/NuSea – J/  polarization (unpublished: hep-ex/ ) E815/NuTeV – neutral current charm production (unpublished) * E781/SELEX – doubly-charmed baryons – Phys. Rev. Letters 89 (2002) * E781/SELEX – D s production asymmetry – PLB 558 (2003) 34 * E791 – D* production asymmetry and polarization – PLB 539 (2002) 218 * E831/FOCUS –  c and  c production asymmetries (unpublished) * E831/FOCUS – DD correlations – PLB 566 (2003) 51 See Matteo Negrini’s talk on charmonium production

SELEX reported possible signals for 3 doubly-charmed baryon states (May 2002) ISMD 2003 Erik Gottschalk The  c + K    state was published in Phys. Rev. Lett. 89, (2002) ccd + candidate at 3520 MeV/c 2 three independent analyses find the same signal wrong-sign combination with K + shows no peak

SELEX reports possible signals for 5 doubly-charmed baryon states (Hadron 2003)

SELEX observations on the production of doubly-charmed baryon states Erik Gottschalk Decay properties: four narrow states all decay weakly lifetimes < 33 fs (expected fs) photon coupling must be highly suppressed different L means level split is not due to spin-flip Production issues: ~ 20% of  c + are produced by ccd(3520) decay doubly-charmed baryons are produced by baryon beams within statistics, protons are at least as effective as   in producing these states FOCUS has ~ 12x more  c + events than SELEX, and does not see doubly-charmed baryons in a wide range of decay modes E791 (  beam) has 5x as many  c + events, and does not see doubly-charmed baryons “confirmation (or refutation) in other hadron experiments is crucial…”

Charm Production Asymmetries A  _______ = ________  c   c N c  N c  c   c N c  N c ISMD 2003 Erik Gottschalk Since perturbative QCD has not been able to account for production asymmetries (see Tom Mehen’s talk), the best tools we have available now are models that can reproduce existing experimental data so that these models can be used to study charm production. Perturbative QCD calculations predict very small charm production asymmetries. Fixed-target experiments often observe large asymmetries for charm particles, and the asymmetries are often attributed to the “leading particle effect.” A leading particle (L) has valence quark(s) in common with the beam (or target) particle.

D s Asymmetry from E791 (500 GeV  - ) & E781/SELEX (  ,  , p beam) E791   beam (D s asymmetry) E781/SELEX   beam (D s asymmetry) ISMD 2003 Erik Gottschalk

D* Asymmetry from E791 (500 GeV  - ) & E781/SELEX (  ,  , p beam) E791   beam (D* asymmetry) E781 Preliminary ISMD 2003 Erik Gottschalk E781/SELEX   beam (D* asymmetry)

Charm Baryon Production Asymmetries from E831/FOCUS (180 GeV  beam) ISMD 2003 Erik Gottschalk Default Pythia Data Default Pythia Data E831/FOCUS Preliminary Asymmetry comparisons to default Pythia E831/FOCUS Preliminary E831/FOCUS  c + asymmetry First measurements of production asymmetries for  c baryons Pythia (with default settings) is not able to reproduce these asymmetries … another test for the Heavy Quark Recombination model? See Tom Mehen’s talk on heavy flavor production

Charm-pair events in FOCUS (180 GeV  beam) ISMD 2003 Erik Gottschalk Normalized D mass vs. normalized D mass Yield = 7066 ± 119 KK    KK DD D0D0 primary vertex (N Primary = 5) The FOCUS sample of DD events was reconstructed using the decay modes D 0  K -  +, D +  K -  +  +, D 0  K -  +  +  -, and charge conjugate modes. Except for a few minor discrepancies, P YTHIA does an excellent job of modeling photoproduced charm-pair events. DD Mass (GeV/c 2 )  (3770)? Cuts: N Primary = 2 no energy in EM calorimeters

Results for fully-reconstructed charm pairs ISMD 2003 Erik Gottschalk  (radians) p t 2 (DD) (GeV/c) 2 DD Mass (GeV/c 2 )  y = y D - y D FOCUS data and P YTHIA are in good agreement. Part of the improvement compared to earlier P YTHIA versions is due to larger transverse momentum for initial partons (intrinsic k T ). P YTHIA 5.6: = (0.44 GeV) 2 P YTHIA 6.203: = (1 GeV) 2 * FOCUS Data PYTHIA (default settings) PYTHIA parent distribution

Results for fully-reconstructed charm pairs ISMD 2003 Erik Gottschalk  (radians) p t 2 (DD) (GeV/c) 2 DD Mass (GeV/c 2 )  y = y D - y D FOCUS data and P YTHIA are in good agreement. Part of the improvement compared to earlier P YTHIA versions is due to larger transverse momentum for initial partons (intrinsic k T ). P YTHIA 5.6: = (0.44 GeV) 2 P YTHIA 6.203: = (1 GeV) 2 * FOCUS Data PYTHIA (default settings) PYTHIA parent distribution

Results for partially reconstructed charm pairs ISMD 2003 Erik Gottschalk  (radians) p t 2 (DD) (GeV/c) 2 * FOCUS Data PYTHIA (default settings) PYTHIA parent distribution = 1 GeV 2 D* +     K +     ~ D 0 D _ (recoil) _

Future charm-pair studies from FOCUS Preliminary Normalized D s mass vs. normalized D mass Yield ~ 300 FOCUS studies of photoproduced DD events show good agreement between data and P YTHIA (except for a few discrepancies). Is P YTHIA able to reproduce D s D and  c D data as well? Preliminary Can FOCUS do any more studies for doubly charmed baryons? Study charm-pair events with same-sign kaons? Charm pairs with opposite-sign kaons:

 (bb) production cross section and prospects for a new measurement from HERA-B production of doubly-charmed baryons from E781/SELEX production asymmetry measurements from E781/SELEX, E791, and E831/FOCUS charm-pair correlations from E831/FOCUS Summary I have shown recent results from fixed-target experiments on beauty and charm production. I would like to thank the following people for help in obtaining these results: Jeff Appel (E791) Robert Kutschke (E831/FOCUS) Michael Leitch (E866/NuSea) Michael Medinnis (HERA-B) Stephen Pordes (E835) Jim Russ (E781/SELEX) Kevin Stenson (E831/FOCUS) Cecilia Uribe (E831/FOCUS) ISMD 2003 Erik Gottschalk