Multiplicity associated to highpTevents and multiplicity fluctuations

Abstract

It is shown that the difference between the multiplicity associated to high p T events and the unbiased multiplicity is given by the normalized variance of the multiplicity distribution, as a consequence of high p T events being selfshadowed. We discuss the possibility of checking the nonmonotonic behavior with centrality of the normalized variance by measuring the difference between multiplicities. PACS number(s): 25.75.Nq, 12.38.Mh, 24.85.+p In the last few years very interesting phenomena related to high p T physics have been observed at RHIC experiments [1,4], namely, a strong supression of inclusive high p T hadron production in Au-Au central collisions compared to the scaling with the number of binary nucleon-nucleon collisions. The data [6] also show the disappearence of back-to-back jet-like hadron correlations in Au-Au collisions, contrary to what is observed in d-Au and p-p collisions, and a nonmonotonic behavior of the fluctuations in transverse momentum and multiplicity [6-9] with a maximum around low centralities. In order to explore further the physical phenomena involved [10], different correlations related to high p T events are being studied.High p T events are self-shadowed [11]. In this paper we show that due to this property the difference between the multiplicity associated to high p T events and the total multiplicity is directly related to the variance of the multiplicity distribution. In this way, the observed dependence on centrality of the normalized variance can be translated into the difference between multiplicities. In particular, the supression of the normalized variance at large centrality will correspond to a decrease in the difference between multiplicities with increasing centrality.The behavior of the normalized variance has been explained in the string percolation approach as a consequence of the dependence on centrality of the number of clusters with different number of strings. At low centrality there is no overlapping of strings, all the clusters have only one string and the fluctuations arise only from the multiplicity ditribution of one string. As the degree of centrality increases, clusters of different number of strings are formed giving rise to different multiplicity distributions due to the different color of the clusters and therefore different cluster tensions. Now, there are additional fluctuations coming from the different distributions. Above the percolation threshold, essentially only one large cluster is formed and again the fluctuations are suppressed. In this approach, the formation of such a large cluster implies that both multiplicities will be equal, independently of the hardness of the event.We start our discussion by describing hadron-hadron, hadron-nucleus, and nucleus-nucleus collisions, which we label HH, as a superposition of independent elementary interactions. We are specifically interested in such collisions involving an elementary interaction or process of type C. We shall say that a particular HH collision or event is of type C if at least on...

Prospects of Searching for (Un)particles From Hidden Sectors Using Rapidity Correlations in Multiparticle Production at the LHC

“…Correlations between the charged-particle multiplicity in one hemisphere versus that of the other have been extensively studied in a wide range of center-of-mass energies, from bubble chamber experiments to LEP and Tevatron (see [33,34] and references therein) for different beams and targets, in particular to understand the dynamics of dense matter in heavy-ion collisions [121,122].…”

Multiplicity, transverse momentum, forward-backward long range correlations and percolation of strings

“…This assumption is not justified for heavy nuclei collisions at RHIC energies where collective interactions, such as percolation of strings, are at work. However, it can be argued [27] that even in these cases, eq. (2.1) is approximately valid, considering the collision as a superposition of different clusters of elementary interactions (strings).…”

“…Since high p T events are self-shadowed, from eq. (2.1), we can write the difference between the average multiplicity associated to high p T events < n > C and the total average multiplicity in terms of the scaled variance of the total multiplictiy distribution [27]:…”

Investigation of high p t events in nucleus-nucleus collisions using the Hijing event generator

“…It has been shown by Cunqueiro, Deus and Pajares [2] that the difference between the multiplicity associated to high p t events and unbiased multiplicity is given by the normalised variance of the unbiased multiplicity indicating thereby the self-shadowing of the high p t events. We here reproduce some of the equations of ref.…”

“…We here reproduce some of the equations of ref. [2] for the sake of clarity. In hadron-nucleus collisions, the inelastic unbiased cross section is defined as:…”