Transcript Slide 1
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 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
F
2
D
( 3 ) (
x IP
, ,
Q
2 ) H1 Collaboration
Mairon Machado – CBPF – july 2008
Diffractive Process
• • Rapidity (y) gaps no particle production Hadron-hadron collisions 1%
y
1 2 ln
E
E
p z p z
• Pomeron p z 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) X Inclusive DIS: Probes partonic structure of the proton • • • Q 2 : 4-momentum exchange W: p center of mass energy x: fraction of p momentum carried by struck quark • x IP : fraction of p momentum carried by the Pomeron (IP) Diffractive DIS: Probes structure of the exchanged color singlet
x IP
q
(
p q
p p
' )
Q
2
Q
2
M
2
X
W
2
• β: fraction of IP momentum carried by struck quark X
Ingelman-Schlein model
2
q
(
Q
2
p
p
' )
Q
2
Q
2
M
2
X
x x IP
Mairon Machado – CBPF – july 2008
Inclusive process
• Cross section for a process in which partons of two hadrons (A and B) interact for assoc iated J/ ψ+γ production • •
p
x a
p
p
and x b
J
/
X d
1 8
dx
are the momentum fraction of nucleons
d
b f a
/
p
(
x a
)
f b
/
p
(
x b
)
d t
carried by the partons f i/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 P T distributions of leptons in J/ ψ diffractive cross section • f g/IP is the gluon distribution in the Pomeron - experimental parametrization • to Pomeron structure function (H1) and f
IP/ p
Inclus ive cross section x
IP
= 1 is the Pomeron flux
Mairon Machado – CBPF – july 2008
Singlet and octet cross sections
u
ˆ
m
2
s x
1
E
P T
sh
• • Partial decay width = 0 .05084
e c 2 =2/3; M ψ = 3.096 GeV; α s = g s 2 / 4 π
E
m
2
P T
2
ch
2
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
d
2
b
|
A
(
s
,
b
) | 2
d
2
b
|
P s
(
b
,
A
(
s
,
b
) | 2
s
) •
A(s,b)
is the amplitude (in the parameter space) of the particular process of interest at center-of-mass energy
s
•
P S (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 proton Pomeron 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
inc tot diff tot • 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