Report

Diffractive J/ψ+γ Production at Collider Energies Mairon Melo Machado High Energy Phenomenology Group, GFPAE IF – UFRGS, Porto Alegre [email protected] www.if.ufrgs.br/gfpae Motivations • Study of inclusive and diffractive cross section p p p J / X • Study of the color-octect mechanism based on the factorization formalism of nonrelativistic quantum chromodynamics (NRQCD) • Study of Pomeron trajectory • Study of hard diffractive process • • phenomenology describes the diffractive scattering Ingelman-Schlein model Investigation of the effects from multiple Pomeron scattering gap survival probability factor Analysis using recent parametrization for Pomeron structure function F2D(3) ( xIP , , Q2 ) H1 Collaboration Mairon Machado – CBPF – july 2008 Diffractive Process • Rapidity (y) gaps • Hadron-hadron collisions no particle production 1% 1 E pz y ln 2 E pz • pz Pomeron proton momentum exchange of vacuum quantum numbers • Measured also at HERA (DESY) collider (H1 and Zeus Collaboration) • DDIS contributes substantially to the cross section events 10% of visible low-x Mairon Machado – CBPF – july 2008 Diffractive DIS at HERA 1 COVOLAN, R. J. M., SOARES, M. PRD 60, 054005 (1998) Inclusive DIS: Probes partonic structure of the proton 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) Diffractive DIS: Probes structure of the exchanged color singlet x IP q ( p p' ) Q 2 M X2 2 q p Q W 2 • β: fraction of IP momentum carried by struck quark X Q2 Q2 x 2 2q ( p p' ) Q M X2 xIP Ingelman-Schlein model Mairon Machado – CBPF – july 2008 Inclusive process •Cross section for a process in which partons of two hadrons (A and B) interact for associated J/ψ+γ production d b dt • xa and xb are the momentum fraction of nucleons carried by the partons p p p J / X d 18 dxa dx f a / p ( xa ) f b / p ( xb ) • fi/h is the parton distribution function (PDF) of a parton of flavor i = a,b in the hadron h = A, B 2 COOPER, F. et al PRL 93 (2004) 171801 Mairon Machado – CBPF – july 2008 J/ψ Diffractive cross sections • 3 XU, J. S. AND PENG, H. A.. PRD 59 (1999) 014028 PT distributions of leptons in J/ψ diffractive cross section • 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 Mairon Machado – CBPF – july 2008 Singlet and octet cross sections uˆ m2 s x1 E PT sh • Partial decay width • ec2=2/3; M = 3.096 GeV; ψ = 0.05084 αs = gs2 / 4π E m2 PT2ch2 4 CHO, P., LEIBOVICH, A. PRD 53, 6203 (1995) Mairon Machado – CBPF – july 2008 Gap Survival Probability (GSP) 5 MACHADO, M. M., GAY DUCATI, M. B. MACHADO, M. V. T. PRD 75, 11403 (2007) • 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 | S | 2 2 2 s d b | A ( s , b ) | P (b, s) 2 2 d b | A ( s , b ) | • A(s,b) is the amplitude (in the parameter space) of the particular process of interest at center-of-mass energy s • PS(s,b) is the probability that no inelastic interactions occurs between hadrons scattered Mairon Machado – ENFPC - 27/09/2007 KMR and GLM models 6 Khoze-Martin-Ryskin Eur. Phys. J. C. 26 229 (2002) • GSP KMR multiple channels • pion-loop insertions in the Pomeron trajectory • non-exponential form of the protonPomeron vertex (t) • absorptive corrections, associated with eikonalization • 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 % Mairon Machado – CBPF – july 2008 Results LHC Tevatron inctot difftot • Black upper lines (inclusive singlet) red dashed bottom lines (diffractive singlet) • Octet contibution domains (near of total value) • 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%) Mairon Machado – CBPF – july 2008 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