Slide 1

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 18   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  m2  s x1 E  PT sh 
• Partial decay width
• ec2=2/3; M = 3.096 GeV;
ψ
 = 0.05084
αs = gs2 / 4π
E  m2  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

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