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 Effectswhere 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 constantMaximum 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!
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