role of gluons in soft and semi-hard p-p collisions at lhc

ROLE OF GLUONS in SOFT and SEMI-HARD P-P COLLISIONS AT LHCROLE OF GLUONS in SOFT and SEMI-HARD P-P COLLISIONS AT LHC

June 2011 1

Gennady Lykasov*,Vadim Bednyakov*, Andrey Grinyuk*,Martin Poghosyan***JINR, Dubna, **CERN

OUTLINEOUTLINE

1. Gluon distribution in proton 2. Quark –Gluon-String Model (QGSM) and gluons in proton.

3. Inclusive spectra of charge hadrons in p-p within QGSM including gluons

4. Elastic parton-parton scattering and semi-hard p-p collisions 5. Summary

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UN-INTEGRATED GLUON DISTRIBUTION UN-INTEGRATED GLUON DISTRIBUTION IN PROTON IN PROTON

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2 2 2 200 0 02

3( , , ) ( ) exp( ( ) )

4t t ts

xg x k Q R x k R x k

where R0=C1(x/x0)λ/2

K.Golec-Biernat & M.Wuesthoff, Phys.Rev. D60, 114023 (1999)H.Jung, hep-ph/0411287, Proc. DIS'2004 Strbske Pleco, Slovakia

2 20 0 1 2 1( , , ) ( ) ( )(1 ) exp( ( ) )gb a

t g t txg x k Q C Q R x x k C R x k

DIAGRAMS in DIAGRAMS in pppp collisions within QGSMcollisions within QGSM

pp

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Fig. 1. The one-cylinder graph (at the left) and the multi-cylinder graph (at the right) for the inclusive pp hX process.

Fig.2. One-Pomeron exchange (left) and the cut one-Pomeron exchange (right); P-proton, g-gluon, h-hadron produced in PP

Inclusive hadron production in central region and the AGK cancellation

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V.A.Bednyakov, A.A.Grinyuk, G.L., M.Poghosyan, hep-ph/0224591 (2011).

2

0

( 0, ) (0, ) ( 1) ( )

(0, )( ( / ) )

g t g t nn

g t nd

x p p n s

p g s s

01

( 0, ) (0, ) ( ) (0, ) ( / )q t q t n q tn

x p p n s p g s s

3

30

( , ) ( , )(1 )( / )

ndq t g t

d NE y p y p

dp g s s

( , ) exp{ }q t q q ty p A b p ( , ) exp{ }g t g t g ty p A p b p

February 2011, JINR 7

Parton - parton interactions within LO QCD, the wavy line is the gluon, the solid line is the quark.

;)/ln()233(

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ˆ 2222

2

21

Qn

Qd

dA

std

d

fs

ijs

ij

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The inclusive spectrum of charge hadrons in p-p at y=0. The gluon distribution at low transverse momenta was calculated and the parameters were found to describe the LHC data satisfactorily. V.A.Bednyakov,A.A.Grinyuk,G.I.Lykasov, M.G.Poghosyan, hep-ph/0224591 (2011);

2 20 0 1 2 1( , , ) ( ) ( )(1 ) exp( ( ) )gb a

t g t txg x k Q C Q R x x k C R x k

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The unintegrated gluon distribution at x = 10-4

Hannes Jung, hep-ph/0411287, 2004.

SUMMARY

1. The soft QCD or the QGSM describes the experimental data on inclusive spectra of charge hadrons produced in p-p at low pt (< 1 GeV) rather satisfactorily

2. The inclusion of the gluon distributions in proton allows us to apply the QGSM to analyze the hadron production in p-p at higher transverse momenta (~ 2 GeV)

3. Starting from ~ 2 GeV hard processes dominate: Field, Feynman, Fox model and perturbative QCD.

4. The unintegrated gluon distributions in proton at low intrinsic transverse momenta were calculated and parameters were found fitting the LHC data.

5. At large intrinsic transverse momenta they should coincide to the distributions found by GBW, J.Hannes and others.

THANK YOU VERY MUCH FOR THANK YOU VERY MUCH FOR YOUR ATTENTION !YOUR ATTENTION !

We also thankWe also thank A.Bakulev, V.Cavasini, A.Dorokhov, A.V.Efremov, A.Bakulev, V.Cavasini, A.Dorokhov, A.V.Efremov,

F.Francavilla, C.Gwenlan, H.Jung, V.Kim, F.Francavilla, C.Gwenlan, H.Jung, V.Kim, N.Kochelev, E.A.Kuraev, LN.Lipatov, T.Lomtadze, N.Kochelev, E.A.Kuraev, LN.Lipatov, T.Lomtadze,

M.Mangano, C.Merino, S,V.Mikhailov, E.Nurse, M.Mangano, C.Merino, S,V.Mikhailov, E.Nurse, F.Palla, E.Pilkington, A.F.Pikelner, C.Royon, F.Palla, E.Pilkington, A.F.Pikelner, C.Royon,

M.G.Ryskin, E.Sarkisyan-Grinbaum, O.V.Teryaev, M.G.Ryskin, E.Sarkisyan-Grinbaum, O.V.Teryaev, Yu.Shabelski and V.V. Uzhinskiy Yu.Shabelski and V.V. Uzhinskiy

for very useful discussions and comments.for very useful discussions and comments. June 2011 12

aπ = 0.4 BF = 2.8 BQ = 4.5

aK = 0.04 BF = 2.3

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So, the inclusive spectrum is presented in the following form:

Aq = 11.91 ± 0.39, bq = 7.29 ± 0.11Ag = 3.76 ± 0.13 bg = 3.51 ± 0.02

pt GeV

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