martin zur nedden, hu berlin qwg meeting, nara 2008, p. 1 charmonium production in media martin zur...
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Martin zur Nedden, HU Berlin QWG Meeting, Nara 2008, p. 1Charmonium Production in Media
Charmonium Production in Media
Martin zur NeddenHumboldt-Universität zu Berlin
for the HERA-B Collaboration
International Workshop on
Heavy Quarkonia 2008December 2 – 5 2008, Nara Women University, Japan
Quarkonia in Media / Production
Martin zur Nedden, HU Berlin QWG Meeting, Nara 2008, p. 2Charmonium Production in Media
920 GeV protons
p + A X , s = 41.6 GeV
The HERA-B Experiment
data taking up to march 2003
Spectrometer at the HERA storage ring: proton-fixed target
Martin zur Nedden, HU Berlin QWG Meeting, Nara 2008, p. 3Charmonium Production in Media
Contents
• Introduction• HERA-B Detector• J/ψ: Kinematical Distributions• J/ψ: Nuclear Dependence• χc Production
Martin zur Nedden, HU Berlin QWG Meeting, Nara 2008, p. 4Charmonium Production in Media
Contents: Part 1
• Introduction• HERA-B Detector• J/ψ: Kinematical Distributions• J/ψ: Nuclear Dependence• χc Production
Martin zur Nedden, HU Berlin QWG Meeting, Nara 2008, p. 5Charmonium Production in Media
Hadronic Production of Heavy Quarks
ij
FRijFjFi dxdxppxfxf 2122
212
22
1 ),,,(ˆ),(),(
production in hadronic interaction
Parton-Density-Functionwithin the hadron
partoniccross setion
hadronisation:formation ofhadrons withheavy quarksor quarkonia stats
factorisation of the process
Martin zur Nedden, HU Berlin QWG Meeting, Nara 2008, p. 6Charmonium Production in Media
Quarkonia Formation
Hadronization: formation of Quarkonia (J/ψ, ψ’, χc, Υ)long distance (~1/(mcv)) process:non-perturbative calculations andinput from experiments needed, model dependence:CSM, COM, CEM, NRQCD
qq formation: production of heavy quarks in mediashort distance (~1/mc) / high momentum process:perturbative calculation
Martin zur Nedden, HU Berlin QWG Meeting, Nara 2008, p. 7Charmonium Production in Media
based on Glauber-model:
≠ 1 „dependence”
Nuclear Effects for Charmonium Production
p
μ/e+
μ/e-
J/
final state formation effects:• nuclear absorption• comover absorption• multiple scattering + energy lossinitial state effects:
• shadowing (nuclear PDFs)• parton energy loss • intrinsic charm
ApNpA
HERA-B: acsess to production in media measurement of using C and W wires:
C
W
W
C
W
C
C
W
C
W
C
W
AA
LL
NN
AA
ln
ln
ln
ln
Martin zur Nedden, HU Berlin QWG Meeting, Nara 2008, p. 8Charmonium Production in Media
xF-Dependence of Nuclear Effects
for c = 0.5 fm
xF [fm]
0.2 30
0 10
-0.2 4
p
μ/e+
μ/e-
J/
formation time and length: (xF) = c
= (xF) boost of J/ w.r.t. nucleus
Martin zur Nedden, HU Berlin QWG Meeting, Nara 2008, p. 9Charmonium Production in Media
Contents: Part 2
• Introduction• HERA-B Detector• J/ψ: Kinematical Distributions• J/ψ: Nuclear Dependence• χc Production
Martin zur Nedden, HU Berlin QWG Meeting, Nara 2008, p. 10Charmonium Production in Media
HERA-B Detector and Trigger
p-beam
z [cm]
C
Ti
W
Muon-TriggerElectron-Trigger
Martin zur Nedden, HU Berlin QWG Meeting, Nara 2008, p. 11Charmonium Production in Media
•150 M di-lepton trigger events (e+e- / μ+μ- triggers) ~ 300 000 J/ψ ~ 15 000 c
~ 5 000 ψ’
• 210 M minimum bias events
HERA-B Data Samples
m(ee) [GeV/c2]
en
trie
s/(3
0 M
eV
/c2)
103
104
2.5 3.0 3.5 4.0
~ 120 000 J/ψ ~ 2 200 ψ′
σJ/ψ ~ 64 MeV
~ 120 000 J/ψ ~ 2 200 ψ′
σJ/ψ ~ 64 MeV
e+e-
J/J/ψψJ/J/ψψ
ψ′ψ′ψ′ψ′
en
trie
s/(2
5 M
eV
/c2)
m(μμ) [GeV/c2]
103
104
2.8 3.2 3.6 4.0
μ+μ-
J/J/ψψJ/J/ψψ
ψ′ψ′ψ′ψ′
~ 170 000 J/ψ ~ 3 000 ψ′
σJ/ψ ~ 44 MeV
~ 170 000 J/ψ ~ 3 000 ψ′
σJ/ψ ~ 44 MeV
Three target materials:pC,pW and pTi collisions
absolute cross section measurements for di-lepton triggered data need independent reference cross section
measured with minBias events: σ(J/ψ) = (502 ± 44) nb/nucl.
Martin zur Nedden, HU Berlin QWG Meeting, Nara 2008, p. 12Charmonium Production in Media
Contents: Part 3
• Introduction• HERA-B Detector• J/ψ: Kinematical Distributions• J/ψ: Nuclear Dependence• χc Production
Martin zur Nedden, HU Berlin QWG Meeting, Nara 2008, p. 13Charmonium Production in Media
J/ pT Distributions
HERA-B combined result
Increase of <pT2> with
A (radius of nucleus):
linear dependence on the nuclear path length of the incident parton
GeV1.29/4.27s
GeV8.38s
GeV6.41s
NA50
E672/706/771/789
HERA-B
2
2
2
11
T
TT
T p
pp
dp
dN
Martin zur Nedden, HU Berlin QWG Meeting, Nara 2008, p. 14Charmonium Production in Media
J/ψ xF - Distribution
Fx
FF
F w
xx
dx
dN2lnexp
wxF : widthΔxF : shift
width increasing withRadius of nucleus
shift increasing withRadius of nucleus
• pT distribution:• increase of <pT
2> with radius• xF distribution:
• increasing width and shift with radiusboth effects compatible with initial state energy loss
HERA-B combined result
Martin zur Nedden, HU Berlin QWG Meeting, Nara 2008, p. 15Charmonium Production in Media
Contents: Part 4
• Introduction• HERA-B Detector• J/ψ: Kinematical Distributions• J/ψ: Nuclear Dependence• χc Production
Martin zur Nedden, HU Berlin QWG Meeting, Nara 2008, p. 16Charmonium Production in Media
Measurement of Nuclear Dependence
TF
C
C
TF
W
W
C
W
TF
dpdx
ddpdx
d
A
Apx
/1
/1
ln
ln
1)/(
XJpAA /
sys.stat. 016.0004.0981.0
C
W
C
W
A
A
nuclear dependence parameter α extracted from the ratioof carbon and tungsten J/ψ production cross sections
Final result form HERA-B:
result based on double wire runs only
Measurement of the xF and pT dependence of α based on full data sample:
Using the measured kinematical distributions of carbon and tungsten (normalized)(full data sample of single and double wire runs)
Martin zur Nedden, HU Berlin QWG Meeting, Nara 2008, p. 17Charmonium Production in Media
Nuclear Dependence Measurement: pT
Good agreement of E866 anHERA-B measurement in thecommon region of pT
pT broadening effect as seen by E866 confirmed
Martin zur Nedden, HU Berlin QWG Meeting, Nara 2008, p. 18Charmonium Production in Media
Theoretical Models for xF Dependence
Separate description and integration:
• final state absorption• interaction with co-movers• energy loss (EL)• shadowing of nuclear PDFs• intrinsic charm quark components (IC)
Nuclear Parton Density Functions:
• Eskola, Kolhinen, Salgado (EKS, Eur.Phys.JC9(1999)61)• scale dependence of a proton within a nucleon via DGLAP• initial PDF from CTEQ4L and LO-GRV
• Eskola, Paukkunen, Salgado (EPS, arXiv:0802.0139)• improved leading order DGLAP including NLO
• Hirai, Kumano, Nagai (HKN, Phys.Rev.C70(2004)044905)• nuclear structure functions and Drell-Yan cross sections• weak anti-shadowing at negative xF
Initial state energy loss:
• Gavin, Milana (GM, Phys.Rev.Lett.68(1992)1834)• based on multiple scattering approach• elastic scatterings of quarks and gluons
• Brodsky, Hoyer (BH, Phys.Lett.B298(1993)165)• modification of GM
Model calculation by R. Vogt:
- Phys.Rev.C61(2000)035203- Phys.Rev.C71(2005)054902- Private communication
Martin zur Nedden, HU Berlin QWG Meeting, Nara 2008, p. 19Charmonium Production in Media
Theoretical Descriptions: Overview
All calculations done by Ramona Vogt in 2007/2008
Martin zur Nedden, HU Berlin QWG Meeting, Nara 2008, p. 20Charmonium Production in Media
Nuclear Dependence Measurement: xF
average α measurement form HERA-B:
sysstat 016.0004.0981.0 .
Final result form HERA-B, to be published in Eur.Phys.J
Martin zur Nedden, HU Berlin QWG Meeting, Nara 2008, p. 21Charmonium Production in Media
Reggeon Phenomenology Model
Boreskov and Kaidalov (JEPT Lett.D77(2003)599):
predicts anti-screening effects in negative xF region- color less state containing quarks (i.e. D-Mesons) propagates trough the nucleus- large size (consisting of D-mesons), large interaction cross section: energy loss- J/ψ projected out of energy dependent color-less state
HERA-BE866
cc
HERA-B result within uncertainties qualitatively compatible
Martin zur Nedden, HU Berlin QWG Meeting, Nara 2008, p. 22Charmonium Production in Media
Contents: Part 5
• Introduction• HERA-B Detector• J/ψ: Kinematical Distributions• J/ψ: Nuclear Dependence• χc Production
Martin zur Nedden, HU Berlin QWG Meeting, Nara 2008, p. 23Charmonium Production in Media
χc Production
)/(
)/()(2
1,
J
JBRR i
cic
c
Relative measurement of χc to J/ψ production
eeJ
Jc
//
/
HERA-B:
Selection by γ Selection (Eγ) andinvariant mass measurement: )()( llMllMM
• making use of J/ψ production cross section from min.Bias data• disentangle χc1 and χc2 by double Gaussian fits: separate cross section measurements• background subtraction by mixed events• separate analysis for electrons and muons• full statistics in both channels: 15000
Martin zur Nedden, HU Berlin QWG Meeting, Nara 2008, p. 24Charmonium Production in Media
χc Event Counting
electronsmuons
Separation of χc1 and χc2 in the ΔM spectra:• double Gaussian fit with some fixed parameters predicted by MC• free parameters are the ratio and sum of event numbers
Martin zur Nedden, HU Berlin QWG Meeting, Nara 2008, p. 25Charmonium Production in Media
A-Dependence
C
W
C
W
J
A
A
R
R
c
c
c
log
log
/
averaged result of
HERA-B:
Δα = 0.05 ± 0.04
Atomic mass number dependence:
• same principle as for J/ψ• no significant difference in A-dependence within the statistical limits
Martin zur Nedden, HU Berlin QWG Meeting, Nara 2008, p. 26Charmonium Production in Media
Production Cross Section Ratio R(c)
[GeV]s
CDF CDF ((p-pp-p))
ISR ISR ((p-pp-p))
E771 E771 ((p-p-SiSi))
E705 E705 ((p-p-LiLi))
E369/ E369/ 610/ 610/ 673 673
((p-p-BeBe))
2002/3 final
ππ-A-A
Final result: Rχc = (18.8 ± 2.8)%
of the produced J/ψ’s come from χc decays
HERA-B
HERA-B 2000
[%]c
R
97015200)(#
6605630)(#
7109570)(#
tot
ee
c
c
c
available statistics:
Martin zur Nedden, HU Berlin QWG Meeting, Nara 2008, p. 27Charmonium Production in Media
Final Results of χc
eon61)nb/nucl(231)(
nb/nucleon)35133()(
23.057.0)(
)(
04.005.0
40.002.1
188.0
c2
1
2
1
12
028.0026.0
c
c
c
R
Rc
Final result form HERA-B, accepted for Phys.Rev.D (arXiv:0807.2167)
Martin zur Nedden, HU Berlin QWG Meeting, Nara 2008, p. 28Charmonium Production in Media
Summary
HERA-B collected 300000 J/, 15000 χc and 220 Mio minimum bias events on nuclear targets (mainly carbon and tungsten)
Final Results on charmonium production:
• J/: inclusive production cross section• J/: xF and pT distributions in a new negative xF range J/: nuclear dependence: tendency of enhancement in at xF <0• c : production ratio, disentanglement of χc1 and χc2
Final results on kinematics of J/ production, nuclear dependence of J/ψ and c production are final and published (during 2008)
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