1. EXPERIMENTAL REVIEW OF DISORIENTED CHIRAL CONDENSATES
Bedanga Mohanty
Variable Energy Cyclotron Centre, Kolkata
OUTLINE
Motivation
Experimental Signatures
Experiments
Experimental Techniques
Experimental Results
Possibility and Limitations
Summary
Bedanga Mohanty

2. MOTIVATION Possibility of it’s restoration for a hot and dense matter
Chiral Symmetry is broken in ground state
Possibility of it’s restoration for a hot and dense matter
One of the consequence of this is
formation of disoriented chiral
condensates
Study and detection of DCC :
Nature of chiral phase transition
Vacuum structure of strong interaction
A.A. Anselm et al., PLB 261(1991) 482
Rajagopal et al NPB 404 (1993)577
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3. EXPERIMENTAL SIGNATURE
Ch. particles vs. Photons
Look at Ng vs. Nch correlation
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4. COSMIC RAY EXPERIMENTS
It all started with the detection of a Centauro Event by JACEE Collaboration
One of the possible explanation of such events was DCC
PAMIR experiment (1977 – 1991) has given, so far the most direct evidence of DCC formation in cosmic ray events
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5. NUCLEON-NUCLEON COLLISION
UA1 experiment at s = 540 GeV p - p¯ collisions
Electromagnetic and Hadronic calorimeters
UA5 experiment at s = 540 and 900 GeV p - p¯ collisions
Streamer chamber for charged particles (4 coverage)
Photons measured by putting a converter between 2 streamer chambers
D0 and CDF at FERMILAB s = 1.8 TeV
Looked at asymmetry in hadronic and electromagnetic energies
MINIMAX at FERMILAB s = 1.8 TeV p - p¯ collisions
Charged particles detected through MWPC
Photons through PbSc electromagnetic Calorimeter
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6. NUCLEUS-NUCLEUS COLLISION
WA98 at CERN SPS
Center of Mass Energy = 17.3 GeV
Ion : Pb beam on Pb target
Photon and charged particle multiplicity detector with common  coverage between 2.9 to 3.75
STAR and PHENIX at RHIC
PMD/EMCAL with TPC/FTPC in STAR
EMCAL and drift and pad chambers in PHENIX
NA49 at CERN SPS
Through measurement of charged particles in more than 2m long TPC
pT coverage from GeV/c to 1.5 GeV/c and  between 4 to 5.5
ALICE at CERN LHC
PMD and FMD
PHOS and TPC
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7. TYPICAL EXPERIMENT FOR DCC SEARCH
SPMD : 2.35 < h < 3.75
PMD : 2.9 < h < 4.2
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8. EXPERIMENTAL TECHNIQUES
Several experimental techniques were devised to specifically look for DCC and several already existing ones were modified for DCC purposes
Photon-charged particle correlation
Discrete Wavelet Technique
Robust Observable
Event Shape Analysis
Phi-measure
Photon-to-charge ratio fluctuation
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9. PHOTON AND CHARGED PARTICLE CORRELATION
Plot event-by-event Nch Vs. Ng
Get the perpendicular distance of each point from the Correlation line
Get the distribution of these distances
Broader the distribution more is the fluctuation
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10. DISCRETE WAVELET TECHNIQUE
B.K. Nandi, T.K. Nayak, B. Mohanty, D.P. Mahapatra and Y.P. Viyogi Phys. Lett. B461 (1999) 142
Define photon fraction in highest resolution bins
Choose a basis (Haar, D4..)
Look at the distribution of the father function coefficients (FFC) at different scales
Broader the FFC distribution more is the fluctuation
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11. Fi = <N(N-1)…(N-i+1)> / <N>i
ROBUST OBSERVABLES
Developed by the MINIMAX collaboration, called as robust, as it take cares of detector effects
Strong correlation between Ri,1 Vs. i for DCC-type events; absent for normal events
Ri,1 = Fi,1 / Fi+1,0
Fi = <N(N-1)…(N-i+1)> / <N>i
Fi,j = <Nch(Nch-1)..(Nch-i+1)Ng(Ng-1)..(Ng-j+1)> / <Nch>i <Ng>j
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12. EVENT SHAPE ANALYSIS Uses flow technique to look for DCC
B.K. Nandi, G.C. Mishra, B. Mohanty, D.P. Mahapatra and T.K. Nayak Phys. Lett. B449 (1999) 109
Uses flow technique to look for DCC
Basic point exploited is event shape of DCC
Can be used as a complimentary method along with other techniques
Bedanga Mohanty

13. -MEASURE
B. Mohanty, Int. J. Mod. Phys. A18 (2003) 1067
  has been modified to make it sensitive for DCC-type fluctuations
 ~  <N><f2> - <f>(1-<f>)
-measure is an observable widely used for fluctuation studies and is defined as
<Z2>/<N> - <z2>
z = x - <x> : single particle variable and Z = multi-particle analog
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14. DDCC = 1.8 A FLUCTUATION PROBE FOR DCC where We define:
B Mohanty, D. Mahapatra and T.Nayak Phys.Rev.C 66 (2002)
We define:
where
Fluctuation in the ratio, R :
The average is over events and
DDCC = 1.8
This difference is significant and provides a
powerful method of DCC search.
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15. COSMIC RAY RESULTS
C.R.A. Augusto et al., Phys. Rev. D59 (1999)
Solid triangles : PAMIR data
Solid squares : Generic production
Do not exclude the possibility of DCC formation mechanism
In high energy interactions
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16. NUCLEON-NUCLEON  UA5 RESULTS
K. Alpgard et al., (UA5 Collab.) Phys. Lett. B115 (1982) 71
G.J. Alner et al., (UA5 Collab.) Phys. Lett. B180 (1986) 415
<R>
Charged particle ET
Photons
<R> = Ehad – Eem / Ehad + Eem
Correlation of charged multiplicity and photon multiplicity
Upper limit on Centauro events = 0.24%
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17. NUCLEON-NUCLEON  UA1 RESULTS
G. Arinson et al., (UA1 Collab.) Phys. Lett. B122 (1983) 189
data
Simulation
Electromagnetic energy
Electromagnetic energy
No DCC
Hadronic energy
Hadronic energy
Correlation between electromagnetic energy and hadronic energy
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18. NUCLEON-NUCLEON  MINIMAX RESULTS
T.C. Brooks et al., (MINIMAX Collab.) Phys. Rev. D 61 (2000)
R(1,1)
1.026  0.004
R(2,1)
1.035  0.010
R(3,1)
1.059  0.027
R(4,1)
1.118  0.065
R(5,1)
1.310  0.151
R(6,1)
1.904  0.382
Pure DCC : R(1,1) ~ 0.6 – 0.7
Exclusive production : Event either DCC or generic
Associated production : DCC production proportional to
Generic production
Upper limit on DCC production
DCC event per generic event < 0.21
Probability an event is DCC < 0.05
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19. NUCLEUS-NUCLEUS  WA98 RESULTS
Ref : Phys.Lett.B420: ,1998
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20. NUCLEUS-NUCLEUS  WA98 RESULTS
Ref : PRC 64 (2001) (R)
Top 5% central events ONLY
Bins in f : 1,2, 4, 8, 16
Discrete Wavelet Analysis
Correlation Analysis:
Results from data compared to mixed events and simulation
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21. NUCLEUS-NUCLEUS  WA98 RESULTS
Ref : PRC 67 (2003)
B. Mohanty, P. hD Thesis Utkal University
Fluctuations in both : Ng & Nch
Localized fluctuations decrease
from central to peripheral.
Upper limit for DCC-like
localized fluctuations: 3x10-3
for central collisions.
Bedanga Mohanty

22. NUCLEUS-NUCLEUS  WA98 RESULTS
M.M. Aggarwal (WA98 Collab.), Pramana 60 (2003) 987
An event with 90° patch
having ƒ = 0.7
Preceding and
Succeeding events normal
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23. NUCLEUS-NUCLEUS  NA49 RESULTS
H. Appelhauser et al., (NA49 Collab.) Phys. Lett. B 459 (1999) 679
Momentum fluctuation  DCC
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24. NUCLEUS-NUCLEUS  PHENIX RESULTS
Typical Centauro event
Reported by PHENIX
+ charged particles
O photons
T. Nakamura (PHENIX Collab.)
Poster at QM2002
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25. POSSIBILITIES AND LIMITATIONS
B. Mohanty et. al : Int. J. Mod. Phys A19 (2004) 1453
DCC MODEL : Introduce DCC-type fluctuations in
VENUS event generator by isospin flipping of pions
with the probability Domain defined in
terms of its extent in pseudo-rapidity and azimuthal
angle
Method of analysis :
Wavelets
Signal/Background
Signal (S) :
of DCC distribution
Background (B) :
of normal distribution
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26. LIMITATIONS - I Charge excess events affected
Shift in f-distribution in the lower range
Effect more for smaller domains of DCC
Charge excess events affected
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27. Correlation due to contamination masks signal
LIMITATIONS - II
Multiple domain, detector effects and charged particle contamination in photons
Correlation due to contamination masks signal
Multi-domains – Following Central limit Theo. f-dist approaches normal distribution
Realistic efficiency and purity of particle detection shrinks f-distribution
Bedanga Mohanty

28. POSSIBILITIES - I
Multiplicity of pions and sensitive analysis techniques
Carrying out analysis by dividing the phase space helps in case of multiple domains of DCC
Higher Multiplicity reduces the statistical fluctuations
Bedanga Mohanty

29. POSSIBILITIES - II Better to analyze events with higher f values
Knowing the purity – effect can be corrected
Effect of charged particle contamination in photon sample can be reduced
Better to analyze events with higher f values
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30. POSSIBILITIES - III Charge excess Vs. Photon excess events
Better to look for events with photon excess
Bedanga Mohanty

31. Momentum information of particles
POSSIBILITIES - IV
Momentum information of particles
Charged particle detector with particle-wise momentum information + a photon multiplicity detector is the best option
Bedanga Mohanty

32. SUMMARY Look for PHOTON excess events, within different pT regions
Experiment
Collaboration
CM Energy
Search Region (η,φ)
1980
Mt. Chacaltaya
Brazil-Japan
√s≧1.7 TeV
1992
Balloon
JACEE
5.0<η<9.0
⊿φ<2π
1991
Mt. PAMIR
PAMIR
------
1982
SPPS
UA5
√s=540 GeV
|η|<5.0
1983
UA1
|η|<3.1
1986
√s=900 GeV
1996
TEVATRON
CDF
√s=1.8 TeV
|η|<4.2 ,⊿φ<2π
1997
MINIMAX
3.4<η<4.2
1998
SPS
WA98
√s=3.5 TeV (Pb+Pb)
2.90<η< 3.75
⊿φ<π
2001
RHIC
PHENIX
√s=39.4 TeV (Run2) (Au+Au)
|η| < 0.35
⊿φ<1/2π (×2 arm)
Exotic events
DCC ??
Null results
Upper limit
Look for PHOTON excess events, within different pT regions
Using a multi-resolution technique
Strange DCC ?? – Gavin, Kapusta
Isospin fluctuations in kaons
Bedanga Mohanty

33. MOTIVATION Chiral Symmetry is broken in ground state
Possibility of it’s restoration for a hot and dense matter
Through search for disoriented
chiral condensates
Study and detection of DCC :
Nature of chiral phase transition
Vacuum structure of strong interaction
A.A. Anselm et al., PLB 261(1991) 482 Rajagopal et al NPB 404 (1993)577
Bedanga Mohanty