1 diffractive heavy quark production in aa collisions at the lhc at nlo* mairon melo machado gfpae ...
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Diffractive heavy quark production in AA collisions at the
LHC at NLO*Mairon Melo Machado
GFPAE – IF – UFRGSmelo.machado@ufrgs.br
www.if.ufrgs.br/gfpae
* Work with M. V. T. Machado and M. B. Gay Ducati
DIFFRACTION 2010 – OTRANTO, ITALY, 10 – 15 SEPTEMBER
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Outlook Motivation
Diffractive Physics
Hadroproduction of heavy quarks at LO
Hadroproduction of heavy quarks at NLO
Coherent heavy quark production
Pomeron Structure Function
Multiple Pomeron Scattering
Results
Conclusions
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Heavy quarks will be produced in large quantities at LHC
Very important for physics study and for understanding background processes
Heavy flavoured hadrons may produce high momentum leptons
Potential background to new physics
Estimate the inclusive, single and Double Pomeron Exchange (DPE) in heavy ion collisions
Coherent and incoherent (single diffraction) production of heavy quarks in AA collisions
Coherent DPE production of heavy quarks in AA collisions
Motivation
BBH BBgg
signal
background
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A+[LRG]+A+XA+A *A+[LRG]+A+XA+A
A+[LRG]XQQLRGAA+A ][][
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Introduction Diffractive processes caractherized by a rapidity gap Pomeron
Pomeron and its reaction mechanisms is not completely known
Regge Theory Pomerons with substructure DPDFs
It does not describe hadron collider data
Application of multiple Pomeron scattering suppress the diffractive cross section
Gap Survival Probability (GSP) to AA collisions ?
Diffractive structure function Gap Survival Probability (GSP)
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Studies
1 M. B. Gay Ducati, M. M. M, M. V. T. Machado, PRD 75, 114013 (2007)
2 M. B. Gay Ducati, M. M. M, M. V. T. Machado, PRD 81, 054034 (2010)
1, 2
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Absence of hadronic energy in angular regions Φ of the final state
Hard diffractive factorization 4
Diffractive eventsRapidity gaps
4 M. Heyssler, Z. Phys. C 73. (1997) 297.5 B. Z. Kopeliovich et al, Phys. Rev. Lett. 85, 507 (2000)
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Single diffraction DPE exchange
Introduction of the appropriate absorptive effects which cause the suppresion of any LRG process 5 and nuclear effects as well
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o Focus on the following single diffractive processes
Heavy quark hadroproduction
o Diffractive ratios as a function of energy center-mass ECM
X+cc+ppp X+bb+ppp
o Diagrams contributing to the lowest order cross section 6
6 M. L. Mangano et al, Nucl. Phys. B 373, 295 (1992)
Q+Qg+g
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Total cross section LO
Partonical cross section
are the parton distributions inner the hadron i=1 and j=2
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6 M. L. Mangano, P. Nason, G. Ridolfi Nucl. Phys. B373 (1992) 295
factorization (renormalization) scale RF μμ
x1,2 are the momentum fraction sxxs 21
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NLO Production6
6 M. L. Mangano, P. Nason, G. Ridolfi Nucl. Phys. B373 (1992) 295
g+Q+Qg+g
Running of the coupling constant
n1f = 3 (4) charm (bottom)
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NLO functions8 P. Nason, S. Dawson, R. K. Ellis Nucl. Phys. B303 (1988) 607
a0 0.108068
a1 -0.114997
a2 0.0428630
a3 0.131429
a4 0.0438768
a5 -0.0760996
a6 -0.165878
a7 -0.158246
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Auxiliary functions
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Diffractive cross section
Pomeron flux factor
Pomeron Structure Function (H1) 9
β= xxIP
9 H1 Coll. A. Aktas et al, Eur. J. Phys. J. C48 (2006) 715
KKMR model <|S|2> = 0.06 at LHC single diffractive events 10
10 V. A. Khoze, A. D. Martin, M. G. Ryskin, Eur. Phys. J. C18, 167 (2000)
Parametrization of the pomeron flux factor and structure function H1 Collaboration
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Nuclear single diffractive
11 N. M. Agababyan et al Phys. Atom. Nucl. 62, 1572 (1999)
12 K. Tuchin, arXiv:0812.1519v2 [hep-ph] (2009)
A+[LRG]+A+XA+A
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Inclusive case
APb = 208 (5.5 TeV)
Incoherent process Pomeron emmited by a nucleon inner the nucleus
Coherent process Pomeron emmited by the nucleus
*A+[LRG]+A+XA+A
Diffractive case
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Inclusive nuclear cross section at NLO
APbPb = 208 (5.5 TeV); 40 (6.3) TeV
Heavy quarks production at the LHC
Heavy quarks cross sections in NLO to pp collisions
GSP value decreases the diffractive ratio (<|S|2> = 0.06)
difrativo
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Diffractive cross sections @ LHC
Predictions to cross sections possible to be verified at the LHC 13
Inclusive cross section
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Diffractive cross sections
Very small diffractive ratio
Proton-Nucleus collision
Nucleus-Nucleus collision
13 M. Gay Ducati, M. M. M, M. V. T. Machado, PRD. 81, 054034 (2010)
Similar results that 14
14 B. Kopeliovich et al, 0702106 [arXiv:hep-ph] (2007)
0287.02 GAPS
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Diffractive cross sections @ LHC
No values to <|S|2> for single diffractive events in AA collisions
Estimations to central Higgs production <|S|2> ~ 8 x 10-7
Values of diffractive cross sections possible to be verified experimentally
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13 M. Gay Ducati, M. M. M, M. V. T. Machado, PRD. 81, 054034 (2010)
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Bialas-Landshoff approach
nucleon form-factor
Double Pomeron Exchange
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pQQppp
Differential phase-space factor
mass of produced quarks
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15 A. Bialas and W. Szeremeta, Phys. Lett. B 296, 191 (1992)
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Bialas-Landshoff approach
two-dimensional four-vectors describing the transverse component of the momenta
Sudakov parametrization for momenta
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momentum for one of exchanged gluons
momenta for the incoming (outgoing) protons
momentum for the produced quark (antiquark)
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Bialas-Landshoff approachSquare of the invariant matrix element averaged over initial spins and summed over final spins 14
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effect of the momentum transfer dependence of the non-perturbative gluon propagator
14 A. Bialas and W. Szeremeta, Phys. Lett. B 296, 191 (1992)
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DPE results
Ingelman-Schlein
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Bialas-Landshoff
pp collisions at the LHC (14 TeV)
10 V. A. Khoze, A. D. Martin, M. G. Ryskin, Eur. Phys. J. C18, 167 (2000)
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Ingelman-Schlein > Bialas-Landshoff
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Conclusions• Theoretical predictions for single and DPE heavy quarks production at
LHC energies in pp, pA and AA collisions
• Diffractive ratio is computed using hard diffractive factorization and absorptive corrections (NLO)
• There are no predictions to <|S|2> in pA and AA collisions
• Diffractive cross sections for AA collisions possible to be verified
• Diffractive channel dominates over exclusive photoproduction channel in proton-proton case
• Calculation of GSP values to AA collisions is highly importantDIFFRACTION 2010
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pA cross sections @ LHC
Suppression factor
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σpA ~ 0.8 mb
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