hadron production spectra in collider experiments
DESCRIPTION
Hadron production spectra in Collider Experiments. Andrei Rostovtsev Moscow, ITEP. Low-x Meeting, June 2010. There exists a large body of high precision experimental data on hadron production in high energy particle collisions. Transverse Momentum Spectra of Charged Particles. - PowerPoint PPT PresentationTRANSCRIPT
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Andrei RostovtsevMoscow, ITEP
Low-x Meeting, June 2010
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There exists a large body of high precision experimental data on hadron production in high energy particle collisions.
Collisions Energy Range Experiments
Proton – Proton 23 – 2360 GeV ISR, SppS, CDF, CMS
Gamma - Proton 200 GeV H1, ZEUS, Omega
Gamma - Gamma 100 GeV Opal, L3
DIS 120 – 213 GeV
7 < Q2 < 28 GeV2
H1, ZEUS
Aurum - Aurum 200 Gev RHIC
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A single smooth Tsallis-type
function for the whole kinematical
region
Transverse Momentum Spectra of Charged Particles
(Differential Invariant Cross-Section)
NkinT
NTE
Ay
pd
dE
)1()0(
3
3
mmpE TkinT 22
TE kinTe / nkinTE )(
1
A common statistical distribution in the
Nature.
Ekin [GeV]
T Nonperturbative
thermodynamics pQCD
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Does Tsallis-type power law distribution really describe the hadron production spectra?
To answer this question let’s plot a ratio = data / fit function
RHIC Au-Au
NGeVs /200
Observed systematic defects require to modify the fit function
These defects are hidden on usual logarithmic plots!
SppS p-p
GeVs 630
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A modification of the Tsallis function
Take two contributions: Exponential + Power law functions
The best fits are given by
)/)(exp( eT TPF NT TNPF )/)('1/(1 )(', 32
TTkinTT PorPnotEorPFF With scalar
NTe
kinTe TNPATEA )/1/()/exp( 2
exp Power law
SppS p-p
Generalized forms:
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Look back at the Ratios = data / fit function
RHIC Au-Au
NGeVs /200
RHIC Au-Au
NGeVs /200
SppS p-p
GeVs 630
SppS p-p
GeVs 540
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A strong correlation between the fit-function parameters
NTe
kinTe TNPATEA )/1/()/exp( 2Fit-function:
T [
GeV
2]
Te [GeV]
T=18.11Te2
The observed correlation might indicate that the exponential and power law terms are integral parts of more complicated function describing the statistical distribution.
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Modified spectrum fit-function. Interpretation.
Exponential term – “thermolized” hadrons, or a hadronic cloud accompanying the interactions. Boltzmann-type.
Power-law term – originates from partonic hard interactions?
NTe
kinTe
T
TNPATEAydP
d)/1/()/exp()0( 2
2
Ne bNAA )/1/()exp( 2
e
T
T
Ewith
The modified function could be rewritten as:
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The fit-function parameter map
NTe
kinTe
T
TNPATEAdP
d)/1/()/exp( 2
2
T=18.11Te
2T [
GeV
2]
N
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Observations made with the fit parameter map
1. There are two distinct trends:• with change of √s in pp• for different colliding particles and fixed √s
2. The two trends cross each other in a point • with √s = 200 GeV in pp and Au-Au• for minimum bias centrality in Au-Au
3. DIS, p, sit on the same band as Au-Au with different centralities and look similar to very peripheral Heavy Ion interactions
Surprise:
Heavy Ion low centrality (multiplicity) presumably very peripheral interactions differ significantly from single pp-interactions and at the same time are “close relatives” of interactions with photons.
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Further observations: relative contributions of the exponential and power-law terms in
the spectraPower law term fraction in pp spectra as function of √s
• In pp interactions: exp / power-law ≈ 4 independent of √s • Power-law fraction has maximum at mid centralities in Heavy Ion int.• What is about “point-like” ineractions?
Power law term fraction as function of centrality in Au-Au at √s=200 GeV
pp, pp
√s [GeV]
fract
ion
fract
ion
Centrality [%]
Au-Au
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Inclusive J/Ψ production doesn’t leave any room for the exponential term in the spectrum shape
exp
J/Ψ
In DIS, p, the power-law contribution dominates (~100%)fr
act
ion
√s [GeV]
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χ²/ndf = 513.8/234 χ²/ndf = 249.1/232
CDF ’09 CDF ’09
More surprises in high-Pt data
21 )//1()//1( 2221112Nkin
TNkin
TT
NTEANTEAdP
d
8.55.8;89.017.0;10/ 21213
21 NNGeVTTAA
Only at CDF?For PT > 80 GeV is of order of inclusive jet cross section
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PH1 ‘96
OPAL ‘06
L3 ‘02
The onset of high-Pt power-law tail in gamma collisions
The onset of the high-PT power-law term is visible for:
PT > 10 GeV in pp - collisions
PT > 4 GeV in p - collisions
PT > 3 GeV in - collisionsDisagreement with CDF jet spectrum & Fragmentation (A.S.Yoon et al)
Two different regimes for charged hadron production?
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Diffraction-type dips in the inclusive particle spectra?
The only two accurate sets of pp-data extended to high PT
SppS pp
GeVs 540 GeVs 1960
CDF pp
Looking forward to see the LHC (7 GeV) spectra soon.
Provocative examples of the data to fit ratio:
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Conclusions:
• the large body of high precision data on hadron production in collider experiments allow systematic measurements of the fine details of the spectra shape;• a simple power law type statistical distribution (Tsllis, kappa, Levy,…) provides a good approximation, but fail to describe the details of spectra shape both al low and high Pt;• a modified statistical distribution is proposed• despite the hadron spectra have been studied for decades, there is a number of puzzles to be solved:
1. Hadron production parameter map2. High PT tails3. Dips
High statistics LHC charged particle spectra.Wanted: