Nuclear Modifications in Saturated Glauber Model from SPS to LHC Energies

Szilveszter Miklós HarangozóZimányi Winter School 2013

Consultant: Dr. Gábor Papp

ELTE – TTKDepartment of Theoretical

Physics

Supervisor:Dr. Gergely Gábor BarnaföldiWigner RCP of the HASDepartment of Particle & Nuclear Physics

pQCD based parton model

• Nucleon-Nucleon reactions

• Factorization: we assume, the process can be factorized into 3 independent phase

pQCD based parton model

• We calculate the cross sections with a convolution described above.

• We characterize the PDFs & FFs as probability density functions, which can not be calculated perturbatively.

Parton Distribution Function (PDF)

hard partonic scattering

Fragmentation Function (FF)

Improving the model

• 40% uncertanity is too much.

• Phenomenological input.

• Parton’s transverse (intrinsic) momenta have been taken into account.

Assume: transverse momentum distribution is Gaussian:

The c.m. energy dependence of

• Comparison of experimental spectra and results of the calculations

• Uncertanities come from the Principle of Minimal Sensitivity

• The model is more sensitive at low pT-s for the parameter

• Take a look at the tendency…

The pT & dependence of

• best fit for every pT value• for a fixed , pT independent

values can be assumed

• best fit for the average pT

• intrinsic transverse momentum seems to decrease

pT dependence of the dependence of the

Good pp reference spectra can be obtained

Proton-Nucleus (pA) collision

• Experience: the yield differs from the expected: atomic number (A) times the one from pp spectra

• Measuring tool: Nuclear Modification Factor (NMF), RpA

• Difference: Nuclear Effects

where is the number of binary collisions

Nuclear Effects

Nuclear Effects

Nuclear Effects

Multiple Scattering

Nuclear Modifications of PDF’s

• Classic and Saturated Glauber model

• Dependence on the impact parameter, b

• Intrinsic transverse momentum distribution broadens:

• Suppression of the yield at low pT-s

• Several parameterizations has been implemented by different groups

Parameters for the saturated Glauber model in pA collisions

Search for the universal Csat constant

Maximum 3-4 collision with CSat ≈ 0.35

Cronin-effect in the saturated Glauber model

Dependency of the Cronin-peak’s maximum against the Atomic number

• ν: number of semihard collisions

• parameters fitted for experiments

• at fixed , peak stays put

Cronin-effect in the saturated Glauber model

Dependency of the Cronin-peak’s maximum against the Atomic number

• shadowing and saturation also suppresses the spectra

• in fully saturated case we get the original dependency

• we can apply a correction to the formula:

The kTpQCD v2.0 code

PDFFFpQCD

The kTpQCD v2.0 code

• Several parameterization can be probed within the same framework

• Original codes has been implemented

• Easy to add new type of PDFs, FFs, etc.

Pro.:

The kTpQCD v2.1 code

eps09s.cpp

Example: New shadowing: EPS09s

Ref.: 10.1007/JHEP07(2012)073

Reconstruction

• HIJING shadowing + Multiple scattering

• EPS09s shadowing

• Both parameterizations gives acceptable results

• For HIJING ν= 4 gives the best fit

• For RHIC results EPS09s is the best

Questions - Motivation

• Which nuclear effects cause the peripheral anomalies?

• Can we model model them?

• To claim a better understand of the Glauber-model

• Find the limits (or a better implementation) of the saturated picture

Summary

• pp reference

• first results on minimum bias collisions

• an updated code with “easy-to-upgrade” properties

We have:

We don’t have: • good enough parameterization for LHC energies

• better understand of the peripheral collisions

• an updated code with “easy-to-upgrade” properties

Thank you for your consideration!