Presentazione di PowerPoint

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Charm, beauty and charmonium production at
HERA-B
A. Zoccoli Università and INFN Bologna For the
HERA-B Collaboration

• Outline
• Detector trigger
• Data sample
• Results from the 2002/3 run
• charmonium production
• open charm
• beauty production
• Summary

Hard Probes 2004 Ericeira, Portugal November
5th, 2004
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The HERA-B Detector
Muon Detector4 layers of gas pixel chambers
(inner) and MWPC with cathode pad readout
(outer), pad-coincidence pretrigger
Top View
920 GeV/c Protons
e/e- beam
Magnet
10 m
0 m
20 m
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The HERA-B detector

• p-Nucleus interactions at 920 GeV
• BX crossing rate 10 MHz ? Up to 4107
  interactions/s (5ev/bx)
• Very sophisticated and challenging detector.
• Large central acceptance ( 5 gt ?lab gt 2 )
• Capability to reconstruct the full event
• Very good particle ID for (e, ?, ?, K, p)
• High resolution vertexing
• Target 8 wires in the p-beam halo
• 5 materials C, Ti, Al, Pd, W
• Double wire configuration for
• A-Dependence Measurements CW
• Online event reconstruction
• Very selective multilevel trigger
• (hardware software) J/? ? µµ/ee

? Suitable for P-Nucleus interaction studies
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Trigger DAQ System
Multilevel trigger scheme based on Kalman filter.
5 (10) MHz
Pretrigger/Level 1 (rejection 250)
(lt12 ms)
Level 2 (rejection. 200)
20 KHz
(5-10 ms)
Full online reconstruction and logging to tape
100 Hz
(1s)
Two PC-Linux farms used in L2 and for the offline
reconstruction.
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Relevant data samples
Data taking finished in 2003. Analysis in progress

• 150 M di-lepton trigger events (ee-/µµ-
  triggers)
• 300 000 J/? (gt1000 per hour)
• 15 000 ?c1 ?c2
• 5 000 ?(2S)
• 210 M minimum bias events
• 1000 ev/s gt1TB/day
• 35 M hard photon events
• 60 M glueball trigger events

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Dilepton spectrum Muon Channel
J/y
Approx. 177,000 eventsMass 3095 MeV/c2Width
44 MeV/c2
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Physics topics

• Topics covered in this presentation
• 1) J/? pT distribution
• J/? xF distribution
• J/? A-dependence
• ?(2s) production
• ?c/J/? production ratio
• FCNC D0 ? µµ Br limit
• bb cross section
• ? production
• Open charm production

J/?
Di-lepton trigger
e e- ? ?-
?(2s)
?C
D0
bb
?(1-3s)
MB data
D0
K?(?)
Disclaimer All results are preliminary
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J/? Differential Distribution pT

• Parametrisation
• Broad pT coverage, good agreement between
  electron and muon channels

80 of ee- sample
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J/? Differential Distribution pT
CEM predictions
FIT result

• Good agreement with the general energy scaling
• Possible comparison with model predictions (e.g.
  curve based on CEM by R. Vogt)

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J/y Differential distribution xF

• Large acceptance for negative xF (fractional
  longitudinal momentum)
• Usual parametrization
• Work on systematics and theory function (?)

10 of ee sample
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J/y A-Dependence

• 3 ingredients of A-dependence measurement

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J/y A dependence
Preliminary
I1I2
I1I2

• Previous result of FNAL E866 extended to xF
  0.35
• Result from 15 of full mm sample, statistical
  uncertainties only, similar results for ee-
• Work on systematics ongoing. Complete the
  analysis on the full data sample.

preliminary
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?(2S) Production

• Measure ?(2S) cross section relative to J/?
  ? reduce systematic uncertainties
• eJ/y/ey(2S) 0.7-0.8 (MC)
• Preliminary results for

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y(2S) differential distributions
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cc Production

• Test of charmonium production models fraction
  R(?c) of J/? from
• radiative decays ?c? J/? ?? µ µ ?
• Signal found in mass difference M(J/? ?) M(J/?)

Where
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cc Production - II
Preliminary result (15 of ?? statistics 1.300
?c) Total expected statistics (ee µµ)
15.000 ?c . ? A-Dep. measurement
R(?c)
R(?c)0.210.05(stat.)
CSM
Average
NRQCD
ECMS

• Results consistent with no ECMS dependency (CEM)
• HERA-B point agrees with NRQCD but NRQCD
  underestimates R at low Ecms

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Open charm production
From Minimum Bias data analysis

• Production Cross Sections for D0, D, D
• Production Ratios D/D0 and D/D0

Assuming Aa dependence with a 1
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Open charm production - II
HERA-B ? Charm 1.5 ?(D0,D)
?mc
?2mc
PYTHIA underestimates D/D0 ratio
Theoretical curves are NLO from R.Vogt
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Open charm production - III
Phythia requires K-factors 1.5 and 4.5 to
describe D0 and D data if mc1.5 GeV Smaller mc
require smaller K factors but predict smaller
increase of ? at higher E
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New Limit on BR(D0????)
BR from SM 10-19

• Search for flavor-changing neutral current decay
  D0???? (branching fraction enhanced in some
  MSSM models 10-7)
• 3 events in signal region
• Phys.Lett.B596173-183,2004)

BR(D0????) lt 2.0?10-6(90 CL)

• Current limits by
• CDF BR(D0????) lt 2.5?10-6 (90 CL) Phys. Rev.
  D68 (2003) 091101
• BaBar BR(D0????) lt 1.3?10-6 (90 CL)
  hep-ex/0408023

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s(bb) inclusive b production
B Meson has a long life time ( 9 mm at HERA-B
kinematics) 0.5 mm dilepton vertex
resolution J/? from a B decay will be detached
from primary interaction
downstream
upstream
Analysis cuts - Decay lenght (?z) - Impact
parameter
Normalization on the inclusive prompt J/? cross
section. ? Systematic error minimization
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open b production

• C,W,Ti targets
• Full statistics
• Unbinned likelihood fit

20 sys. error under investigation, main
contribution Br(bb?J/?X) 2.32?0.20
Lifetime ? (1.41 0.16)ps
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Cross section
Cross section obtained by using E771/E789 results
scaled to 41.6 GeV ?(J/?)357 2 36
nb/nucleon

• Theoretical uncertainties
• b quark mass 4.5 - 5 GeV
• At NLO, scale (m) dependence
• Previous measurements do not agree between each
  other
• Agreement with the previous HERA-B result (1.5 s)

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Upsilon production
pN ?? X, ????-, ee-
- Relative production of ?(1S)/?(2S)/?(3S) fixed
on E605 data - Mass resolution between 140 and
160 MeV/c2 - Normalization on measured J/? or
Drell-Yan cross section - C(75) W(25) targets
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Upsilon production - II
Cross section determination
HERA-B prelim.

• Good agreement with CEM predictions (by R. Vogt)
• - Results compatible with no nuclear
  suppression
• ? 0.99 0.05

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Conclusions

• HERA-B collected 300k J/? events on different
  nuclei
• Preliminary results presented on
• J/ ? cross section, xF and pT distributions in a
  new negative xF range
• J/? A dependence demonstrate a flat behavior in
  this region
• Fraction of ?c and ?(2S) yields relative to J/?
  
• D0, D and D cross sections and relative
  yields
• Limit on FCNC D0? µµ decay
• Open and hidden beauty cross sections
• These results help to constrain theoretical
  calculations
• Final results on these and other topics are
  expected in 2005

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Backup slides
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HERA-B
13 Nations 30 Institutes
150 physicists
IHEP, Beijing U. Tsinghua
Norway
China
U. Oslo
LIP, U. Coimbra LIP, U. Lisbon
Portugal
Denmark
NBI, Copenhagen
ITEP, Moscow JINR, Dubna
Russia
U. Humboldt, Berlin U. Dortmund DESY MPI
Heidelberg U. Heidelberg U. Mannheim MPI
Munich U. Rostock U. Siegen DESY Zeuthen
Slovenia
J.F. Inst, Ljubljani
Germany
Spain
U. Barcelona
U. Zurich
Switzerland
INR, Kiev
Ukraine
U. Texas, Austin U. Cincinnati Wayne State U. U.
Houston U. Calif, Los Angeles
INFN, U. Bologna
Italy
U. Utrecht NIKHEF
USA
Netherlands
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Why Charmonium Production?

• Test of current framework for charmonium
  production models nonrelativistic QCD
  (perturbative expansion in relative quark
  velocities)
• Modification of models via nuclear effects
• Initial state effects, e.g. shadowing, energy
  loss
• Final state effects, e.g. absorption in nuclear
  matter
• Parametrization power law with exponent ?
  ?(xF,pT)? is measure of A-depencence (A
  target atomic mass)? lt 1 charmonium suppression
  by nuclear effects (anomalous suppression
  signature for quark-gluon plasma)

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A-Dependence Theory
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A-Dependence HERA-Bs Contribution

• Measurements in proton-nucleus scattering
  (Fermilab E866/NuSea) as a function of xF

• HERA-B
• Extend kinematic range to xFlt-0.35
• Triggering 2 channels simultaneously e, ?
• 2 materials simultaneously (C, W) ? better
  control of systematic effects

M.J. Leitch et al., Phys. Rev. Lett. 84 (2000)
3256
HERA-B
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cos? differential distribution of J/?
? is the Gottfried-Jackson decay angle
J/? polarization described by ? parameter
15 of ee- sample
? (0,1,-1) (no, trans., long.)
polarization
Important tests for models
HERA-B variation range -0.5,0.1 0.1
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J/? Production Cross Section
signal in minimum bias data
J/? Production cross section as a
function of
HERA-B result is higher than E771/789 Theoretical
description is reasonable but not perfect (fig.
is in a log scale)
Assuming Aa dependence with a 0.955
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?,?-- Searches
(hep-ex/0408048) accepted by Phys. Rev. Lett.
Counts
Counts
B d?/dy ?b/C
B d?/dy ?b/C
UL(95)B?d?/dyy0 4-16 ?b/N _at_ 1521-1555
MeV/c2 ? / ?(1520) lt 3 12
UL(95)B?d?/dyy0 2.5 ?b/N _at_ 1862 MeV/c2 ?--
/ ?- lt 3/B ?-- / ?(1530)0 lt 4/B
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Hard photon analysis
Direct ? production dominant process gq? ?q ?
Unique sensitivity to gluon density function
Main bkg sources, also important to test QCD
pC?pX

• HERA-B
• Widest rapidity range
• Large pT range
• Highest energy for pA
• Ongoing analysis on heavier materials

pC??X
pC??X
(normalization still arbitrary)