Heavy Quark Production in 920GeV Proton Nucleus Interactions Michael Danilov ITEP, Moscow Representing HERA-B Collaboration Outline 1.Detector and data sample 2.Charmonium production 3.Open charm production 4.Hidden and open beauty production 5.Summary

Heavy quark production is not well understood theoretically Experimental data are often scarce or contradictory NRQCD tuned to reproduce Charmonium production at Tevatron describes also γγ data However NRQCD does not describe well charmonium production in: 1. B decays (J/ψ branching and momentum distribution) 2. e+e- annihilation (large J/ψ cc rate at BELLE) 3. e-p interactions (longitudinal momentum fraction) 4. h-N interactions ( fraction, A dependence) There are problems with description of open charm and beauty production Understanding of open and hidden charm production in h-A interactions is mandatory for interpretation of heavy ion experiments HERA-B can make contributions in many areas Introduction

The HERA-B Detector

Data Sample Data taking is finished in 2003; analysis is in progress All results in this talk are PRELIMINARY 210 M minimum bias events 150 M di-lepton trigger events ( J/ψ) MuonsElectrons 35 M hard photon trigger events 60 M “glueball” trigger events

J/ψ Production Cross Section signal in minimum bias dataJ/ψ Production cross section as a function of Assuming A α dependence with α = HERA-B result is higher than E771/789 Theoretical description is reasonable but not perfect (fig. is in a log scale)

J/ψ Differential Distribution vs p T 80% of e + e - sample Broad coverage in p T HERA-B

Power-law parameterization Only runs with C and W wires operated simultaneously(to reduce systematic effects) J/ψ A-dependence Statistical uncertainties only 10% of µ + µ - sample Theoretical description is far from perfect Models differ drastically at negative x F Understanding of J/  A dependence important for interpretation of heavy ion data

ψ(2S) Differential Distributions in x F and p T dσ/dp T 2 dσ/dx F ‹p T > ~ 1.4 stat err 0.1 GeV/c  HERA-B compatible with previous results  Comparable precision  First measurement in the negative x F range

Ψ(2S) Production Production ratio Systematic studies ongoing √s A ( 1.6 ± 0.2 stat )% C (1.8 ± 0.4 stat )% W from electron analysis (compatible results from muons)

Production 10% of 2002/2003 Data After Background Subtraction observed in radiative decay Production ratio Background shape from event mixing 10% of data

Production Published result of 2000 ( Phys. Lett. B561(2003) 61 ) 10% of 2002/2003 data Results consistent with CEM HERA-B point agrees with NRQCD but NRQCD underestimates R at low Ecms E CMS

Open Charm Production Open charm signals in minimum bias data Production Cross Sections for D 0, D +, D *+ Production Ratios D + /D 0 and D *+ /D 0 Assuming A α dependence with α = 1

Open Charm Production Theoretical curves are NLO from R.Vogt  =m c  =2m c PYTHIA underestimates D+/D0 ratio HERA-B:  Charm = 1.5  (D 0,D + )

Open Charm Production Phythia requires K-factors ~1.5 and ~4.5 to describe D 0 and D + data if m c =1.5 GeV Smaller m c require smaller K factors but predict smaller increase of  at higher E Lorenco and Woehri

Beauty Production Look for detached vertices from 35 % statistics Background from min.bias and prompt J/  has smaller IP and  Z

Beauty Production Compatible results from the muon and electron channels Combined result (systematic error 25-30%) 1.5 σ lower than 2000 measurement: (Eur.Phys.J. C26(2003) 345)

 Production BR(   l + l - )  = (3.9±1.1stat) pb/nucl ( μ + μ - ) = (2.9±1.2stat) pb/nucl ( e + e - ) =( 3.4±0.8stat) pb/nucl (combined)  (1S)/  (2S)/  (3S) relative production fixed on E605 data BR(   l+ l- )  α = 0.99 ± 0.05 Data compatible with no nuclear suppression

SUMMARY HERA-B collected 300k J/  events on different nuclei Preliminary results (based typically on 10-30% of statistics) are presented on: J/  cross section, p T and x F distributions in a new negative x F range J/  A dependence demonstrates a flat behavior in this region Fraction of  c and  (2S) yields relative to J/  D0, D+ and D*+ cross sections and relative yields Open and hidden beauty cross sections These results help to constrain theoretical calculations Final results on these and other topics are expected in 2005

Backup Slides

J/ψ Production Cross Section signal in minimum bias data J/ψ Production cross section in pN collisions as a function of Assuming A α dependence with α = HERA-B result is higher than E771/789 but fits well with new PHENIX result

Open Charm Production