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23-09-2004 M.Mevius
Open and hidden beauty production in 920 GeV proton –nucleus
collisions at HERA-B
M.Mevius
DESY
23-09-2004 M.Mevius
Data Sample
• Data taking is finished in 2003; analysis is in progress
additional: 210 M minimum bias events
dilepton trigger:• pretriggers
high ET ECAL clusters, MUON hits • FLT: hardware trigger
track finding behind magnet• SLT: software trigger
track finding behind magnet and in VDSvertex reconstruction
•online event reconstruction 150 M dilepton trigger events 300 000 J/ (>1000 per hour) 10 000 c
3 500 (2S)
23-09-2004 M.Mevius
Dilepton spectra
~ 1600
•Long Tracks (Vertex Detector + Tracking System)•PID: likelihood , E/p•Dilepton Vertex Probability > 1%•J/ acceptance: -0.35 < xF < 0.15
muon channel
~ 108,000 J/ → ee
σ = 64 MeV/c2
/
J/
(2S)
electron channelmuon channel
~ 108,000 J/ ee
σ = 64 MeV/c2
/
J/
(2S)
electron channel
~ 177,000 J/ σ = 44 MeV/c2
~ 3000 (2S)
~ 1600
23-09-2004 M.Mevius
open b production
Experiment E p (GeV) s (nb/ nucleon) N Events
E789 800 5 ± 1.5 ± 3 ~ 20
E771 800 43(+27-17)± 7 ~ 6
HERA-B(2000) 920 32(+14-12)(+6-7) ~ 10
Theory Order
N.Kidonakis et al. NLO + NNLL 30 ± 18
R.Bonciani et al. NLO + NLL 25 (+20-13)
• Theoretical uncertainties: – b quark mass 4.5 - 5 GeV– At NLO, scale () dependence
• Previous measurements do not agree between each other
23-09-2004 M.Mevius
)/(
1
//
XJbbBrn
nzBRJ
BJbb
ss
pn bb + Xb(b) B J/ + X
J/ ; e+e-
open b production
Measurement relative to direct J/ production to minimize trigger/reconstruction uncertainties
R= relative efficiency1
B selection eff. from MC
23-09-2004 M.Mevius
open b production
B Selection: (30-45% Efficiency)Lepton impact to the wire
Distance J/ to wire
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
23-09-2004 M.Mevius
open b production•Vertex z resolution ~ 500 μm •Good agreement between data and MC simulation•good separation between direct and detached J/
Cuts optimized simultaneously
Background:•bb and cc simultaneous semileptonic decays•Combinatorial•Prompt J/
23-09-2004 M.Mevius
open b production
0.027 0.004 0.005/
bb
J
s
s
• C,W,Ti targets
• Unbinned likelihood fit
preliminary
20% sys. error under investigationmain contribution: Br(bbJ/X) = 2.320.20%
23-09-2004 M.Mevius
J/ cross sectionE771/E789 : scaled to HERA-B cms energy s(J/)=357 ± 2 ± 36 nb/nucleon
E771/E789
HERA-B measurement on min. bias data ongoing
using E771/E789 result:
preliminary
9.8 1.4 2.0 nb/nucleonbbs
23-09-2004 M.Mevius
upsilon production
HERA-Bs = 41.6 GeV
E772 (A=2)
E605 (A=64)
• Several measurements available but unclear situation at s ~ 40GeV
• HERA-B has good coverage in the central region of collisions ( xF ~ [-0.35,0.15])
• Theoretical prediction Hadronization: Possible
nuclear suppression ?
23-09-2004 M.Mevius
upsilon production
pA + X
μ +μ- ; e+e-
/
/0
1( ) = ( / ) / ) J
J effy
d NBr l l Br J l l J
dy N y
s s
• Measurement relative to prompt J/ – Less sensitive to systematic effects
• Prompt J/cross section from E771 and E789
23-09-2004 M.Mevius
upsilon production• 25% W + 75 % C (targets)• Mass resolution between 140
and 160 MeV/c2
• Background:
Drell-Yan: shape estimated from MC
(1S) / (2S) / (3S) relative production fixed to E605 results
Random combinatorial: estimated from like sign pairs in data
8
23-09-2004 M.Mevius
upsilon productionEvents Br• ds/dyy=0
+- 33 ± 7 3.9 ± 1.1 pb/n
e+e- 31 ± 10 2.9 ± 1.2 pb/n
both 3.4 ± 0.8 pb/n
• Both channels are compatible• Extrapolation to S = 38.8 GeV yields:
Br• ds/dyy=0 = 2.4 ± 0.9 pb/n– compatible with E605– (more than 1 s) below E772 and E771
23-09-2004 M.Mevius
upsilon production
Not usedin fit
As
ms
dy
dBr o
o
y
exp)(0
ss
• Modified Craigie parameterization to include nuclear suppression (parameter )
• Data compatible with no nuclear suppression:
= 0.99 0.05
23-09-2004 M.Mevius
• HERA-B has finished data taking• preliminary results:
s(bb) :
• using: s(J/)=357±2±36 nb/nucleon
production:
Conclusions
0.027 0.004 0.005/
bb
J
s
s
9.8 1.4 2.0 nb/nucleonbbs
0
( ) = 3.4 0.8 pb/nucleony
dBr l l
dy
s
23-09-2004 M.Mevius
model dependence
• Changing PDFs from MRST to CTEQ• b quark mass from 4.5 to 5.0 GeV/c2
• QCD renormalization scale from 0.5 o to 2 o
• Fragmentation functions– Peterson form with from 0.002 to 0.008– Kartvelishvili form with from 12.4 to 15.0
• <kT2> from 0.125 to 2.0 GeV2
• Fraction of b-baryons produced in the b-hadronization process from 0 to 12%
±1.5% ±1% ±2% ±3%
±1%
±2%
Default model: MRST PDF, Peterson FF =0.006 22222 GeV/c 0.5kpmGeV/c 4.75m TTbb 0
Total: ±5%
Studied variations: Sys cont. to s(bb )