YThermal

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YThermal
D.J .Kim /Y.Kwon YONSEI UNIVERSITY
Tsukuba-Yonsei Workshop Program Inst. of
Physics,Univ. of Tsukuba
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Outline

• Motivation
• Introduction to Thermal Model
• Introduction to YThermal
• Physics Issues of YThermal
• YThermal Howto
• Furture Work

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Motivation
Develop a model calculator for PHENIX
based on the work of P.
BraunMunzinger et al.s work. --- One of
the circumstantial evidence for the QGP formation
is the chemical equilibrium of the
produced hadron multiplicity
including the strangeness sector ( Phys. Lett.
B465, 15-20, 1999 ). --- Rejection or
confirmation of this conclusion will be within
the reach of PHENIX run1
measurements if we can account for
the the kinematics of the whole phase space
properly.    --- Hence we decided to
reproduce the model and study the basic aspects
of the model parameters relavant to
the experiment. ( T, mB ) ,volume correction
--- Proper handling of the whole kinematics
are under progress.
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Thermal Model
GCE strangeness baryon number charge
conservation excluded volume correction
Free Parameter ( T, mB ) volume correction
System Parameter ( N , Z ) Proton,neutron
number of the colliding nuclei
mmass(Chiral symmetry restoration) , rradius
for the volume correction
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As model and data agree very well, one can
assume, that the system is in thermal and
chemical equilibrium at the time of chemical
freeze-out The freeze-out point is characterized
by different temperatures and baryochemical
potentials in the different collision system, but
is very close to the predicted quark-gluon phase
boundary
CERN press Release New State of Matter created
at CERN
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For volume correction
After this, PRC 56,p2210,1997
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Entropy conservation (T, ? s) ?( S, nB )
S/N, nB
Net baryon number
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pi/pi- K/K- pbar/p
pi/p
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Introduction of YThermal

• gtgt Technically the model is built upon ROOT frame
  work (http//root.cern.ch/)
• with two objectives(YThermal, Yparticle )
• First , to generate a user friendly system which
  any PHENIX collaborator can understand and use
  easily.
• This include
•      1. the automatic documentation
•      2. the usage of the object inspector
  graphics
•      3. free usage of the declared classes
• Second, to prepare the model as a part of the
  bigger hydrodynamic model calculation which is
  under steady progress.
• note all units follows hbar c 1
  unless dictated otherwise

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Ythermal HowTo

• memo
•  important input
• (T,mu_B), Btotal
• With (T,mu_B), thermal model predicts the
  absolute particle densities.
• When Btotal ( the baryon umber of the fireball
  ) is decided, it subsequently decides the
  absolute multiplicities of all particles.
  Experimentally Btotal will have close
  relationship with the collision centrality in the
  thermal model.

• 1. Design scheme
• gt Production of the particle objects and simple
  initialization.
•     YThermal thermal new YThermal(0.168,0.266)
  
• gt Decides the baryon number of the fireball
•     thermal-gtSet_Btotal(200)
• gt Input isospin balance for Iz calculation
•    thermal-gtSet_Isobalance(0.66949153)
• gt Set default experimental feed-down
•    thermal-gtExperiment()
• gt Clears data block for each particle species
•    thermal-gtClear()
• gt Perform the iteration and do the calculation
• gt iteration over all particles.
•    thermal-gtDoIt()

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Generation of the html files 1. How to
insall http//ipap.yonsei.ac.kr/npl/thermal/i
nstall.html) After the system is properly
installed, you can load       thermal
(This is root with the dynamic library
for the thermal model calculation ).     then
execute         root 0 .x GenerateHtmlDoc.C
        What's in the html file? You can try
        netscape html/USER_Index.html  
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• Usage of the object inspector
• thermal
• root 0 .x CaseTEST.C
• root 1 gP-gtInspect()
• root 2 TF1 fun1 (TF1 )gPIP-gtFnid
• root 3 fun1-gtDraw()
• gPIP-gtFnid is the pointer to the function used to
  get PIP total multiplicity ( i.e. integrand ). x
  axis correspond to k/m and y axis are the
  integrand function.
• root 4 fun1-gtPrint()
• This shows the parameters of the distribution.
• Par 0 mu/mass
• Par 1 T/mass
• Par 2 eta ( 1 for Fermi stat, -1 for Bose stat
  ).
• If you like to access the model values, you can
  try
• root 5 thermal-gtPrintInfo(0)19
• Each one explains what is being printed...

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YThermal
YParicles
ROOT
STABLE(12) Ythermal.Primary Gamma, pi ,pi-,pi0,
K,K-,p ,n ,pbar,nbar, Deuteron , Deuteron b WEAK
(16)Ythermal.Experiment K0 ,K0b,Lambda,Lambdab,
SigmaP Sigma0 SigmaM SigmaPb Sigma0b SigmaMb
Cascade0 CascadeM Cascade0b CascadeMb, OMEGA
OMEGAb STRONG Ythermal Strong the
others M(mesons)lt1.5GeV M(baryons)lt2 GeV This
limits the temperature upto which thermal model
calculations are trustworthy to Tmaxlt 185GeV (ltgt
heavier hadrons is not sufficiently well known)
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Physics Issues

• 1. Volume correction
• 2. Finding out the most probable (T, mB )
• 3. Particle ratios
• 4. pi pt spectrum
• 5. Weak-decay feed-down and its reconstruction
  efficiency
• 6. Chiral symmetry restoration

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1.Volume correction

• Volume correction is adhoc, but may be needed
  especially when we estimate the absolute particle
  density. However there seems to be possible
  debate on the volume parameter ( PRC 56, 2210,
  1997 , 0.8fm ).
• Change of the volume parameter ruins the
  predictability of the model. The radius
  parameters of the particles has 0.3 fm as the the
  default value as chosen in Phys. Lett. B465,
  15-20, 1999.
• Physicswise volume correction can change the
  relative abundance of particles.
• (volume has to be chosen appropriately to
  simulate the repulsive interactions between
  hadrons)
• As we turn down the volume correcrtion, the
  absolute density increases by almost constant
  factor close to 50 w.r.t the default choice.
  When we change only the pion volume factor, pion
  multiplicity almost exclusively increase. Small
  discrepancy with the red points is due to the
  volume effect of the other particles.

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All particles with r0.3fm pi,pi-,pi0 with
r0 No volume correction(or ideal gas limit)
Number Dendisy
pi
p
K
?
pbar
?(1232)
?(1232)b
charge x mass
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2.Finding out the most probable (T, mB)

• The work of P. BraunMunzinger et al. uses the
  Chi2/DOF as the measure to find the best choice
  for (T, mB ).
• find the most probable (T, mB) for the given set
  of input data. Also the histograms hChi2_ndf0,
  hChi2_ndf1,and hChi2_ndf2 shows Chi2/DOF in three
  different scale.
• As the experimental input, we used the data of (
  Phys. Lett. B465, 15-20, 1999 ). But this
  procedure can be easily modified to any set of
  measurements.
• For this case, we find T 157 (MeV) and mB
  245 (MeV) as the most probable ( though Chi2/DOF
  is not close to 1 ).
• Experimental reconstruction efficiency as
  discussed can play a role. (hyperon,decay
  reconstruction factor, weak decaying neutral
  meson)

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3.Particle ratios

• Particle densities at freeze-out.
• For the RHIC condition, we used (T,mu)
  (0.17,0.01) as used by
• P. BraunMunzinger et al.
• As the data analysis further developes, we will
  be able to conclude on the goodness of the
  thermal model and these parameters.

pbar ? p , K ?K-
Note02 (data?) K ?K- mB small pbar ? p ?
(stopping?)
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4.? pt spectrum

• Integrated pt spectrum assuming
•  1. isotropic fireball  (development in
  progress )
•   2. feed-down from the resonance higher
  mass mesons.
• By running the model,
• we observe rho,omega,Kshort play the
  important role to the pi multiplicity, and
• generate the pair decay spectrum for rho and
  Kshort
• (1/pt dN/dpt distribution with the arbitrary
  normalization.)
• These plots are generated with the 3 different
  reconstruction efficiencies.
• This will be equivalent to changing the
  selection cuts for tracks and studying the pt
• spectral shape assuming the primary
  multiplicity and the kinematics are correct
• ( also we need to assume perfect tracking )
  
• http//www.phenix.bnl.gov/phenix/WWW/p/draft
  /janebh/ talks/pt/global-hadron-092100/outline_092
  100.htm
• Kinematic distributions is affected by the
  hydrodynamic motion and it's likely to be
• included in the next release.
• In fact this will be of importance to the high
  pt particle ( pt gt 2 GeV/c ),
• where description by the perturbative
  physics can be claimed.

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Pt careful study will be needed to get the
proper interpretation ( Weak decay )
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Weak-decay feed-down and its reconstruction
efficiency
Weak-decay feed down efficiency can be handled
and the macro SetWeakDecayFeedDown.C shows how.
We also show the resulting systematics. Particle
list reports c tau values for the following
particles.
To estimate the potential systematics due to
these feed-down, we can vary the reconstruction
efficiencies of the daughter particles ( say 0
SetWeakDecayFeedDownEfficiency0.C,
                   
 50 SetWeakDecayFeedDownEfficiency50.C,
                     and
100 SetWeakDecayFeedDownEfficiency100.C ). For
(T,mu) (0.17,0.01), we can look at these
systematics from the example. N- negative
particles One of the good candidate for the
effect on N- is Kshort. p,pbar is affected from
the feed-down of the hyperons. The effect is less
drastic than the lower energies at CERN and AGS.
At AGS and CERN, mu_B is relatively big and the
consequential mu_S is also relatively big. In the
scheme of hadron thermal model, the abundance of
the multi-strange antibaryon is explained by this
big mu_S.
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Chiral symmetry restoration

• If hadro-chemical transition occurs
• at fairly high Temperature
• ( baryon density is not that high at RHIC ),
• there might be some modification in particle
• properties.
• ThermalChiralSymmetryRestoration.C
• shows how we can change
• the mass of the particles and study the
  effect.

nominal mass excitation mass reduction by 20
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Furture Work

• Address Physics Issues
• Developement of Ythermal including hydrodynamic
  model
• gt Prediction for the kinematic spectrum
• Implementation of the decay into lepton channels