Diffractive Quarkonium Production at High Energies

1
Diffractive Quarkonium Production at High
Energies

• Mairon Melo Machadoa, Maria Beatriz Gay Ducatia,
• Magno Valério Trindade Machadob
• High Energy Phenomenology Group, GFPAE
• aIF UFRGS, Porto Alegre,Rio Grande do Sul
• bUNIPAMPA, Bagé, Rio Grande do Sul
• melo.machado_at_ufrgs.br
• www.if.ufrgs.br/gfpae

VII Latin American Symposium on High Energy
Physics IX Argentinian Symposium of Particles and
Fields San Carlos de Bariloche 14-21 January 2009
2
Motivations

• Study of inclusive and diffractive cross sections
  
• Pomeron plays a particular and very important
  role in soft process at high energy strong
  interaction
• Study of heavy quarkonium production mechanism
• Study the nature of Pomeron in the QCD framework
  
• Investigation of the effects from multiple
  Pomeron scattering
• gap survival probability factor
• Analysis using recent parametrization for Pomeron
  structure function

H1 Collaboration
VII Latin American Symposium on High Energy
Physics IX Argentinian Symposium of Particles
and Fields San Carlos de Bariloche 14-21 Jan 2009
3
Diffractive Process

• Rapidity (y) gaps no particle
  production
• Hadron-hadron collisions 1
• Pomeron carries the quantum
  numbers of the vacuum

pz
proton momentum

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

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

VII Latin American Symposium on High Energy
Physics IX Argentinian Symposium of Particles
and Fields San Carlos de Bariloche 14-21 Jan 2009
4
Diffractive DIS at HERA
Inclusive DIS Probes partonic structure of the
proton

• 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)
• ß fraction of IP momentum carried
• by struck quark

X
Diffractive DIS Probes structure of the
exchanged color singlet
1
X
1 INGELMAN, G. SCHLEIN, P. E. Phys. Lett. B
152, 256 (1985)
VII Latin American Symposium on High Energy
Physics IX Argentinian Symposium of Particles
and Fields San Carlos de Bariloche 14-21 Jan 2009
5
Inclusive process

• Cross section for process in which partons of
  two hadrons (A and B) interact producing
  associated J/?? (??) final states

• xa and xb are the momentum fractions 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

Y, P
2 COOPER, F. et al PRL 93 (2004) 171801
VII Latin American Symposium on High Energy
Physics IX Argentinian Symposium of Particles
and Fields San Carlos de Bariloche 14-21 Jan 2009
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J/? Diffractive cross sections
3 XU, J. S. AND PENG, H. A.. PRD 59 (1999) 014028

• PT distributions of leptons in J/? ( ? )
  diffractive cross section

Y, P

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

VII Latin American Symposium on High Energy
Physics IX Argentinian Symposium of Particles
and Fields San Carlos de Bariloche 14-21 Jan 2009
7
Singlet cross sections

• Partial decay width Gcc 0.05084
• ec24/9 M? 3.096 GeV as gs2 / 4p, mc
  1.5 GeV,
• To ? case mc mb M? MYmb
  4.5 GeV, M? 9.46 GeV
• Gbb 0.0294

4 LANSBERG, J. P., Int. J. Mod. Phys. A 21, 3857
(2006)
5 KIM, C. S., et. al.Phys.Rev. D55 (1997) 5429
VII Latin American Symposium on High Energy
Physics IX Argentinian Symposium of Particles
and Fields San Carlos de Bariloche 14-21 Jan 2009
8
Gap Survival Probability (GSP)?
6 MACHADO, M. M., GAY DUCATI, M. B. MACHADO, M.
V. T. PRD 75, 11403 (2007)?

• Currently a subject of intense theoretical and
  experimental research
• GAP region of angular phase space
  devoid of particles
• Survival probability fulfilling
  of gap by hadrons produced in interactions of
  remanescent particles

7 BJORKEN, J. D. PRD 47, 101 (1992)
8 CHEHIME, H. et al PLB 286, 392 (1992)

• 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 occur between hadrons scattered

VII Latin American Symposium on High Energy
Physics IX Argentinian Symposium of Particles
and Fields San Carlos de Bariloche 14-21 Jan 2009
9
KMR 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
• values of GSP 0.15 (0.09) Tevatron
  (LHC)

9 Khoze-Martin-Ryskin Eur. Phys. J. C. 26 229
(2002)
RY Tevatron ()
0.24
0.13
central
forward
VII Latin American Symposium on High Energy
Physics IX Argentinian Symposium of Particles
and Fields San Carlos de Bariloche 14-21 Jan 2009
10
Results for J/?

• Color-octet is predominant to high pt

VII Latin American Symposium on High Energy
Physics IX Argentinian Symposium of Particles
and Fields San Carlos de Bariloche 14-21 Jan 2009
11
Results for J/?
without GPS R LHC 0.42 R Tevatron 0.61

• J/? production is dominated by gluon-gluon fusion

Average of pseudo-rapidity (central and forward)
VII Latin American Symposium on High Energy
Physics IX Argentinian Symposium of Particles
and Fields San Carlos de Bariloche 14-21 Jan 2009
12
Results for ?
10 Rybarska, A. et al Phys. Lett. B 660, 126
(2008)?
Contribution of ? is smaller than J/? contribution
VII Latin American Symposium on High Energy
Physics IX Argentinian Symposium of Particles
and Fields San Carlos de Bariloche 14-21 Jan 2009
13
Conclusions

• Calculation of J/? ( ? ) diffractive
  hadroproduction process and momentum
  distributions of produced photon
• Using new Pomeron diffractive parton
  distributions (H1 Collaboration DESY HERA)
  and theoretical estimate for GSP
• Ratio diffractive/inclusive cross section falls
  using GSP
• Agreement with another phenomenological
  prediction of 3, 4
• Application of Gap Survival Probability should be
  made
• Useful observable to test future extractions of
  Pomeron PDFs
• J/? production dominates at high energies
  high partial decay
• Color-Octet contributions will be included in
  next work

VII Latin American Symposium on High Energy
Physics IX Argentinian Symposium of Particles
and Fields San Carlos de Bariloche 14-21 Jan 2009