Dcc pdf download

Siemiarczukq , B. Sinhac , N. Slavinef , K. Solomeyd , S. Stankusg , G. Stefanekq , P. Steinbergr , E. Stenlundm , D. Sumberao , T. Svenssonm , M. Trivedic , A. Tsvetkove , C. Tykarskiq , J. Urbahnk , N. Eijndhovenl , W. Heeringenl , G. Nieuwenhuizenr , A.

Vinogradove , Y. Viyogic , A. Vodopianovf , S. Vosl , B. Wyslouchr , K. Yagin , Y. Yokotan , and G. This leads to large imbalances in the production of charged to neutral pions.

Sophisti- cated analysis methods are being developed to disentangle DCC events out of the large background of events with conventionally produced particles. We present a short review of current analysis methods and future prospects. Introduction The QCD phase transition from normal hadronic matter to the Quark-Gluon-Plasma QGP , in case of high energy heavy ion collisions, manifests itself in two forms: 1 Deconfinement transition and 2 Chiral symmetry restoration.

One of the interesting consequences of the chiral transition is the formation of a chiral condensate in an extended domain, such that the direction of the condensate is misaligned from the true vacuum direction. It has been proposed that the decay of the DCC domains would lead to large imbalances in the production of charged to neutral pions. The task for experimentalists is to carefully measure the number of neutral and charged pions as well as study their spectra.

The challenge is to design sophisticated analysis tools on an event-by-event basis to identify DCC amidst the large background due to conventionally produced particles. The formation of DCC domains has been proposed by Anselm[1], by Blaizot and Krzy- wicki[2] and by Bjorken, Kowalski and Taylor[3] in the context of high energy hadronic collisions in order to explain the puzzling Centauro and anti-Centauro type of events ob- served by cosmic ray experiments[5].

Bjorken et al. Rajagopal and Wilczek[4] were the first ones to discuss the DCC phenomena in the context of heavy ion reactions. They have suggested that the nonequilibrium dynamics during the chiral symmetry break- ing phase transitions in case of heavy ion collisions may produce DCC domains. There is tremendous progress [6—12] in terms of theoretical understanding of DCC since then starting with different formalisms.

At low temperatures the chiral symmetry is spontaneously broken. This leads to the isospin symmetry of pions. The field will have to eventually settle in to the true ground state, but oscillations will continue for sometime which leads to amplification of soft pion modes.

Our ability to detect DCC domains depends on the number of domains, size of domains and number of DCC pions emitted from the domains. If the number of domains is more than one, then the distribution given by 2 gets modified, and for a large number of uncorrelated small domains, the resulting distribution becomes gaussian. Clearly the fewer the number of domains and larger the number of emitted pions, the easier it is to detect in the laboratory.

In addition, the probability of DCC formation in a nuclear collision at a given energy is important for the observation of DCC. In this manuscript we will deal mostly with analysis of neutral and charged particle distributions. Other signals which have been proposed for detection of DCC will be discussed towards the end of the manuscript. These experiments have used the technique of the asymmetry of hadronic to electromagnetic energies. So far there is no evidence of any centauro type of events from these experiments.

Results from WA98 experiment will be discussed in detail. The lego acceptance of the detector is a circle of radius 0. The data analysis for DCC search in Minimax is complicated because of small accep- tance of the detector and various efficiency factors which come into play. This method is described in section 5. The results from these data is consistent with no DCC production mechanism.

The experimental setup consists of large acceptance hadron and photon spectrometers, detectors for charged particle and photon multiplicity measurements, and calorimeters for transverse and forward energy measure- ments. At present our search is limited to detailed event-by-event analysis of photon distributions from the Photon Multiplicity Detector and charged particles from Silicon Pad Multiplicity Detectors.

Details of these detectors may be found elsewhere, here we give the essential points necessary for our present discussion. Signals from several neighboring pads are combined to form clusters, characterized by the total ADC content and the hit positions.

Conversely the detector is transparent to high energy photons, since only about 0. Various analysis methods are being employed to characterize unusual events which show up beyond the statistical fluctuations.

All the analysis in WA98 are being carried out in event-by-event basis. In all these analysis, data are not corrected for detector effects and other efficiencies. Instead we compare the data with MC simulations which incorporates all known detector and physics effects. The same method of analysis is followed for both data and MC generated events.

Global Event Characteristics The method of global event characterization in terms of the photon and charged particle multiplicity distributions over the full available phase space is suitable for the search of single large size DCC domain.

The idea here is to look for events which fall far beyond the correlation line of these two distributions. For the current study we have assumed that the DCC could be formed only in central collisions. The central data sample is shown by filled circles in these two figures.

After all cuts are applied, there are events in this sample. A comparison with the MC simulation events chosen by identical cuts for central events is shown by the histogram. The correlation between the charged and neutral multiplicities is presented on the right side of Figure 1 with the minimum bias distribution outlined, the central MC simulated events hatched, and the central data events shown as scattered points, each point cor- responding to a single event.

A strong correlation is seen between charged and neutral multiplicities, which suggests a more appropriate coordinate system with one axis being the measured correlation axis and the other perpendicular to it. This is represented by the Z axis and the DZ axis as shown in figure 1b.

SZ distribution for the data is shown as filled circles in figure 2 a. The histograms show MC simulation results for central events. The hatched region is for MC simulation results. This simulates a DCC accompanied by the normal hadronic background in a way that conserves energy, momentum, and charge. Thus DCC events would appear as outliers with respect to the bulk of the data. Since we do not see no such events in our data sample, we are faced with the possibilities that single-domain DCCs are very rare, very small, or both.

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