Transcript Test of Tevatron Data with H1 Fitter

Anomalous Pion Production
in High Energy Particle
Collisions
Alexander Bylinkin, Andrey Rostovtsev
XV Moscow School of Physics
XXXX ITEP Winter School
14-21 February, 2012
Introduction

Motivation: There exists a large body of experimental
data on hadron production in various experiments.
During its analysis different collaborations treat their data
separately.

It is interesting to analyze this data altogether!
Analyzed Data: Charged pion, kaon, proton and
antiproton spectra produced in:
Collision type
Energy √s
Experiment
pp
53 – 7000 GeV
ISR, UA1, CDF, STAR,
CMS, ALICE
γγ, γp
100-200 GeV
H1, Opal
AuAu
200 GeV
PHENIX
Charge Particle Spectra and the Fit Function
Differential Invariant
Cross-Section
d 3
d 3
d 2
E 3 

d p ddypT dpT
dyd( pT 2 )
Boltzmann
exponent
pQCD
power-law
pT – transverse momentum, y - rapidity
The widely used approximation
d 2
A

2
dyd( pT ) (1  ETkin ) N
T *N
ETkin 
pT2  m2  m
e
New Approach
 ETkin / T

1
( ETkin ) n
A sum of exponential & power-law terms
Why Our Approach is Better?
Defects in the fit with a standard function
Experimental data divided over the values of the fit function in corresponding points
UA1 630GeV
RHIC 200GeV
UA1 630GeV
RHIC 200GeV
d 2
A

2
dyd( pT ) (1  ETkin ) N
T *N
The new parameterization shows much better
approximation of the experimental data.
Anomalies in Pion Production Spectra
Spectra shapes of
pions, kaons and
protons
The relative contribution R
of the exponential and
power-law terms can be
calculated by formula:
R=
exponent
power-law
Power-law _
Exp + Power-law
power-law
No exponent
The sizeable exponential
term contribution exists
only in pion spectra
produced in pp and
heavy ion collisions
Relative contributions of the
exponential and power-law
terms
Relation with Previous Experiments
Particles in hadronic decays of Z-boson
are produced with a probability
described by an exponential function of
the hadron mass squared
π±
Probability divided over the
exponential function:
The pion production is 3 times larger
than it is expected
π±
The ratio R for pions in our analysis equals to ~0.25 which means that
the contribution of the exponential term is 3 times larger than of
the power-law These effects may have the common nature!
Summary



Charged particle spectra produced in various
experiments were analyzed Anomalous
behavior in pion production was observed
Only pion spectra produced in pp and heavy
ion collisions have the sizeable exponential
term
Connection with previous experiments was
discussed Are anomalous behavior found in our
analysis and the excess in pion production
from previous experiments related to each
other?
Thank you for your attention!
Comparison with MC Data
Hypothesis: production of pions via multiple cascade decays results in
the transformation of their spectra into an exponential distribution.
Statement: decay processes are described quite accurately in Pythia
MC generated spectrum for minimum bias
events in pp-collisions at √s = 630GeV
MC and experimental data divided over the fit
function obtained for the experimental spectrum
MC generators don’t reproduce the spectra shape of the experimental data
Correlation Between Parameters
T and Te parameters in the power-law
and exponential terms of the fit function
are strongly correlated with each other
Better approximation is not just a result of exceeding
the number of parameters of the fit function
R Value
The relative contribution of exponential and power-law
terms can be calculated by integrating each term by
transverse momentum from 0 to the upper bound of
the kinematical region
J/ψ Spectra
J/ψ has no exponential term in its spectrum