Diffractive J/ψ+γ Production at Collider Energies

Mairon Melo MachadoHigh Energy Phenomenology Group, GFPAE IF – UFRGS, Porto Alegre

melo.machado@ufrgs.br

www.if.ufrgs.br/gfpae

• Study of inclusive and diffractive cross section

• Study of the color-octect mechanism based on the factorization formalism of nonrelativistic quantum chromodynamics (NRQCD)

• Study of Pomeron trajectory phenomenology describes the diffractive scattering

• Study of hard diffractive process Ingelman-Schlein model

• Investigation of the effects from multiple Pomeron scattering gap survival probability factor

• Analysis using recent parametrization for Pomeron structure function

H1 Collaboration

Motivations

XJppp /

),,( 2)3(2 QxF IPD

Mairon Machado – CBPF – july 2008

• Rapidity (y) gaps no particle production

• Hadron-hadron collisions 1%

• Pomeron exchange of vacuum quantum numbers

Diffractive Process

z

z

pE

pEy

ln2

1

pz

• DDIS contributes substantially to the cross section 10% of visible low-x events

proton momentum

• Measured also at HERA (DESY) collider (H1 and Zeus Collaboration)

Mairon Machado – CBPF – july 2008

Diffractive DIS at HERA

Inclusive DIS: Probes partonic structure of the proton

Diffractive DIS: Probes structure of the exchanged color singlet

X

X

• Q2: 4-momentum exchange • W: p center of mass energy• x: fraction of p momentum carried by struck quark

• xIP: fraction of p momentum carried by the Pomeron (IP)

• β: fraction of IP momentum carried by struck quark

IPX x

x

MQ

Q

ppq

Q

22

22

)'(2

22

22)'(

WQ

MQ

pq

ppqx XIP

Ingelman-Schlein modelMairon Machado – CBPF – july 2008

1 COVOLAN, R. J. M., SOARES, M. PRD 60, 054005 (1998)

Inclusive process

td

dxfxfdxdxd bpbapaba

)()(//

81XJppp /

•Cross section for a process in which partons of two hadrons (A and B) interact for associated J/ψ+γ production

• xa and xb are the momentum fraction of nucleons carried by the partons

• fi/h is the parton distribution function (PDF) of a parton of flavor i = a,b in the hadron h = A, B

Mairon Machado – CBPF – july 2008

2 COOPER, F. et al PRL 93 (2004) 171801

J/ψ Diffractive cross sections

• fg/IP is the gluon distribution in the Pomeron - experimental parametrization to Pomeron structure function (H1) and fIP/p is the Pomeron flux

• Inclusive cross section xIP = 1

• PT distributions of leptons in J/ψ diffractive cross section

Mairon Machado – CBPF – july 2008

3 XU, J. S. AND PENG, H. A.. PRD 59 (1999) 014028

• Partial decay width = 0.05084

• ec2=2/3; Mψ = 3.096 GeV; αs = gs

2 / 4π

Singlet and octet cross sections

shExsmu T12 Pˆ

Mairon Machado – CBPF – july 2008

222 chPmE

T

4 CHO, P., LEIBOVICH, A. PRD 53, 6203 (1995)

Gap Survival Probability (GSP)

22

22

2

|),(|

),(|),(|||

bsAbd

sbPbsAbdS

s

• Currently a subject of intense theoretical and experimental interest

• GAP region of angular phase space devoid of particles

• Survival probability fulfilling of gap by hadrons produced in interactions of remanescent particles

• A(s,b) is the amplitude (in the parameter space) of the particular process of interest at center-of-mass energy

• PS(s,b) is the probability that no inelastic interactions occurs between hadrons scattered

s

Mairon Machado – ENFPC - 27/09/2007

5 MACHADO, M. M., GAY DUCATI, M. B. MACHADO, M. V. T. PRD 75, 11403 (2007)

KMR and GLM models

• GSP KMR multiple channels• pion-loop insertions in the Pomeron trajectory

• non-exponential form of the proton-Pomeron vertex (t)

• absorptive corrections, associated with eikonalization

Mairon Machado – CBPF – july 2008

6 Khoze-Martin-Ryskin Eur. Phys. J. C. 26 229 (2002)

• Average to diffractive ratio predicton for LHC (central) = 0.15 %

• Average to diffractive ratio predicton for LHC (forward) = 0.09 %

• Average to diffractive ratio predicton for Tevatron (central) = 0.48 %

•Average to diffractive ratio predicton for Tevatron (forward) = 0.28 %

Results

Mairon Machado – CBPF – july 2008

LHC

difftot

• Average to diffractive ratio predicton for LHC (central + forward) = 0.12 %

• Average to diffractive ratio predicton for Tevatron (central) = 0.37 %

• Average without GPS - (LHC = 0.42%) and (Tevatron = 0.61%)

Tevatron

• Black upper lines (inclusive singlet) red dashed bottom lines (diffractive singlet)

• Octet contibution domains (near of total value)

inctot

Conclusions

• Analysis of J/ψ diffractive hadroproduction process and rapidity distributions of produced leptons

• Using new Pomeron diffractive parton distributions (H1 Collaboration – DESY – HERA) and theoretical estimate for gap survival factor

• Agreement with another theoretical prediction

• Improvement of data description using gap survival probability

• Useful place to test future extractions of Pomeron PDF’s

• Verification of the factorizatin formalism of NRQCD

• Application of Gap Survival Probability should be made

Mairon Machado – CBPF – july 2008