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Heavy Flavor Production at HERA. - Chapter 6 in arXiv: 0805.3334. Xin Dong. Introduction Measurements of HF production at HERA Production cross sections Structure functions HF production at hadron collider Summary. p. c. p. c. Heavy Production in ep and pp. - PowerPoint PPT Presentation
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1X. DongFeb. 17th, 2011 RNC Group Meeting
Heavy Flavor Production at HERA
Xin Dong
- Chapter 6 in arXiv: 0805.3334
Introduction Measurements of HF production at HERA
Production cross sections Structure functions
HF production at hadron collider Summary
2Feb. 17th, 2011 RNC Group Meeting X. Dong
Heavy Production in ep and pp
LO direct production
c
c
p
p
Heavy flavors are sensitive probes to the initial gluon distributions!
3Feb. 17th, 2011 RNC Group Meeting X. Dong
Production Cross Section
ep
pp
QCD, MQ, Q2 pT
MQ >>QCD in principle, amenable to pQCD calculations.
Q2>>MQ2 heavy quarks are massless
Treatment of heavy quarks in pQCD calculations:
Q2 ~ MQ2 heavy quarks are massive
4Feb. 17th, 2011 RNC Group Meeting X. Dong
Kinematics
Ee, Ee’ : incident positron and scattered positron energye’ : polar angle of scattered positron
x: Bjorken x of photonxg: longitudinal momentum fraction of gluon in proton
5Feb. 17th, 2011 RNC Group Meeting X. Dong
Charm Reconstruction at HERA
STAR 2009 p+p 200 GeVD*
6Feb. 17th, 2011 RNC Group Meeting X. Dong
D* Production Cross Section in DIS
ZM-VFNS: massless charmNot appropriate at low Q2
HVQDIS: massive charmNot correct at high Q2
CASCADE: kt factorization
Insteresting:HVQDIS agrees with data better at high Q2!
7Feb. 17th, 2011 RNC Group Meeting X. Dong
D*-jet-jet production
Angular correlation
Generally agree with NLO QCD- some room to improve in theory
-Hint of high order corrections
D*-jet-jet cross section
8Feb. 17th, 2011 RNC Group Meeting X. Dong
Photon-gluon fusion processes
= 180o
9Feb. 17th, 2011 RNC Group Meeting X. Dong
Charm Structure Function
epeccX
*gcc*cc
probe gluon/charm PDFs
NLO QCD -Extracted from the PDF based on the NLO QCD fit to F2
10Feb. 17th, 2011 RNC Group Meeting X. Dong
HF in Photoproduction
x1, direct processx<1, resolved process
Quasi real photon (Q2~0)Expect pQCD to be applied over the full phase space
D* - jet angular correlation
A good pQCD test - check whether need for higher order terms.
Data/theory comparison indicates some inadequacies of the theory.
x
xg
11Feb. 17th, 2011 RNC Group Meeting X. Dong
HF Production with Vertex Detector
Pointing resolution (H1 vertex detector)
Significance of signed 2D impact parameter (normalized by the resolution)
12Feb. 17th, 2011 RNC Group Meeting X. Dong
Charm and Bottom Structure Functions
13Feb. 17th, 2011 RNC Group Meeting X. Dong
HF Production in Hadron Collisions
At RHIC (mid-rapidity), dominated by the gluon-gluon fusionx range ~ 0.005 - 0.1
LO NLO
gluon splitting
flavor excitation
14Feb. 17th, 2011 RNC Group Meeting X. Dong
Predictive Power for Total Cross Section
10-2 10-110-3 10-2 10-110-3
Important scales in calculating the total charm cross section:mc,
CTEQ6M
=2mc
=mc
=0.5mc
Drastic change of the gluon density function at low Q2
Strong dependence on s
Large uncertainty in predicted total charm cross section (at RHIC)
R. Vogt, LBL SeminarPDFs extracted from inclusive DIS and inclusive jet data.
15Feb. 17th, 2011 RNC Group Meeting X. Dong
Fixed-Order-Next-to-Leading-Logarithm - FONLL
Treat the charm quark as light quarks; should be reliable at pT>>mc
STAR p+p 200 GeV CDF p+p 1.96 TeV
16Feb. 17th, 2011 RNC Group Meeting X. Dong
Summary
Heavy flavors are sensitive probes to gluon distributions in nucleon/nucleus.
Measurements at HERA generally agree with NLO QCD calculations. However larger (x,Q2) region need to be explored and with high precision to constrain the gluon (spin-dependent) density distributions.
More complicated for HF production in hadron collisions. Precision measurements are needed for pQCD test.