122148702
Characteristics of multiplicity distribution of target fragments in forward and backward hemispheres in high-energy nucleus–nucleus interactions
A detailed study on the mechanism of the evaporation of target fragments in the forward and backward hemispheres in 12C–AgBr interactions at 4.5A GeV, 28Si–AgBr interactions at 14.5A GeV, 16O–AgBr interactions at 60A GeV and 32S–AgBr interactions at 200A GeV is carried out in terms of the multiplicity distribution. The nature of the multiplicity distribution in the forward and backward hemispheres is found to be different across all the interactions. The asymmetry parameters and the forward–backward ratios were also calculated for the above-mentioned interactions. The asymmetry parameters and the forward–backward ratios from other nucleus–nucleus interaction data were compared with our results. The forward–backward ratios of target fragments are found to be nearly the same for all the nucleus–nucleus interactions. The forward–backward ratios of all the interactions are greater than 1, suggesting that the probability of emission of fragments in the forward hemisphere is higher than that in the backward direction. The multiplicity moment, entropy and reduced entropy, i.e. the ratio of entropy to average multiplicity of target fragments, are evaluated in both the forward and backward hemispheres for all the four above-mentioned interactions. The values of multiplicity moments are found to be energy independent up to 60A GeV energy in the backward hemisphere. The reduced entropy is also found to be almost energy independent to within experimental error in the backward hemisphere. No such observation can be made in the forward hemisphere. The total entropy of the target fragments is found to be higher in the forward hemisphere. A study of correlation in terms of the scaled variance was also carried out in both the hemispheres for all the nucleus–nucleus interactions. No systematic variation of correlation either with energy or with the size of the projectile nucleus has been noticed. The study yields quite interesting information on the mechanism of particle evaporation in the backward hemisphere.
120905653
NON-STATISTICAL FLUCTUATIONS OF PIONS FOR RING- AND JET-LIKE EVENTS AT CERN SPS ENERGY — AN IN-DEPTH ANALYSIS WITH FACTORIAL CORRELATOR
This study reveals the analysis of ring-like and jet-like events in terms of factorial correlations of 16O–Ag/Br interactions at 60A GeV. The investigation revealed that the correlated moments are found to increase with decreasing bin–bin separation D and follows a power-law which suggests the presence of an intermittent nature of self-similar dynamical fluctuations pattern for ring-like and jet-like events. From the analysis we find that for jet-like events the strength of non-statistical fluctuation is greater than the ring-like and total event set. Jet-like events follow the bin size independence according to α model of intermittency as like total events, whereas ring-like events are not consistent with the prediction of α model of intermittency.
122068137
MULTIPLICITY DISTRIBUTION AND MULTIPLICITY MOMENT OF BLACK AND GREY PARTICLES IN HIGH ENERGY NUCLEUS–NUCLEUS INTERACTIONS
In this paper we have studied the multiplicity distribution of black and grey particles emitted from 16O–AgBr interactions at 2.1 AGeV and 60 AGeV. We have also calculated the multiplicity moment up to the fifth order for both the interactions and for both kinds of emitted particles. The variation of multiplicity moment with the order number has been investigated. It is seen that in the case of black particles multiplicity moment up to fourth order remains almost constant as energy increases from 2.1 AGeV to 60 AGeV. Fifth order multiplicity moment increases insignificantly with energy. However in the case of grey particles no such constancy of multiplicity moment with energy of the projectile beam is obtained. Later we have extended our study on the basis of Regge–Mueller approach to find the existence of second order correlation during the emission of black as well as the grey particles. The second Mueller moment is found to be positive and it increases as energy increases in the case of black particles. On the contrary in the case of grey particles the second Mueller moment decreases with energy. It can be concluded that as energy increases correlation among the black particles increases. On the other hand with the increase of energy correlation among the grey particles is found to diminish.
118199521
Evidence of different reaction mechanisms for hot and cold events in relativistic heavy-ion interaction
This paper reports evidence of different reaction mechanisms for two classes of events, ''hot,'' and ''cold,'' in /sup 12/C emulsion at 4.5 (GeV/c)/N observed by Ghosh et al., from a comparison of the transverse-momentum (P/sub T/) distribution with a mixture of two Maxwell-Boltzmann distributions with different temperatures. The hypothesis is substantiated by the significant difference, for ''hot'' and ''cold'' events, in the values of the average number of pions produced, average emission angle of ..cap alpha..-projectile fragments, and ratio of yield of ..cap alpha.. particles to protons as projectile fragments.
123551661
Entropy scaling in high-energy nucleus–nucleus interactions
We studied the multiparticle production in high-energy nucleus–nucleus interactions in terms of particle entropy in 16O–AgBr and 32S–AgBr interactions at 60 A GeV and 200 A GeV, respectively. An approximate scaling behavior of total produced entropy normalized to maximum rapidity in the center of mass frame measured in different rapidity bins has been reported. The scaling behavior is not supported either by the FRITIOF model or by the Monte Carlo simulated events.
123012389
Multiplicity fluctuations of pions and protons at SPS energy — An in-depth analysis with factorial correlator
We compute the factorial correlators to study the dynamical fluctuations of pions and a combination of pions and protons (compound multiplicity) in 32S-AgBr interactions at 200 A GeV. The study reveals that for both pion and compound multiplicity the correlated moments increase with the decrease in bin-bin separation D, following a power-law, which suggests the self-similarity of multiplicity fluctuation in each case. The results of the analysis also show a consistency with the prediction of α-model for the existence of intermittency in both cases.
118491867
Ultrarelativistic sneutrinos at the LHC and sneutrino-antisneutrino oscillations
Sneutrino-antisneutrino oscillation can be a very useful probe to look for signatures of lepton number violation (ΔL = 2) at the LHC. Here, we discuss the effect of the Lorentz factor γ and the travelling distance L on the probability of the oscillation. We demonstrate that these two parameters can significantly alter the probability of the oscillation when the sneutrinos are ultrarelativistic and have a very small total decay width. We propose a scenario where these requirements are fulfilled and which produces interesting signals at the LHC even for a mass splitting Δm as small as 10 -14 GeV between the sneutrino mass eigenstates.
16299011
Higgs pair production in association with a vector boson at e + e − colliders in theories of higher dimensional gravity
The models of large extra compact dimensions, as suggested by Arkani-Hamed, Dimopoulos and Dvali, predict exciting phenomenological consequences with gravitational interactions becoming strong at the TeV scale. Such theories can be tested at the existing and future colliders. In this paper, we study the contribution of virtual Kaluza-Klein excitations (both spin-0 and 2) in the process $e^+e^- \to HHZ$ and $ e^+e^- \to HH\gamma $ at future linear collider (NLC). We find that the virtual exchange KK gravitons can modify the cross-section $\sigma(e^+e^- \to HHZ)$ significantly from its Standard Model value and will allow the effective string scale to be probed up to 6.6 TeV. The second process is absent at the tree level in the standard model, and can therefore be used to put limits on the effective string scale of 7.4 TeV.
118328469
Collider Signatures for Heavy Lepton Triplet in Type I+III Seesaw
The minimal SU(5) theory augmented by the fermionic adjoint representation restores the coupling constant unification and gives realistic neutrino masses and mixing through the hybrid Type I and Type III seesaw. The crucial prediction of the theory is an SU(2) lepton triplet with the mass below TeV. We study the signature of these heavy leptons and propose the strategy to test this mechanism at the hadron and lepton colliders. The smoking gun evidence of the theory is Delta L=2 lepton number violation through events of a pair of like-sign leptons plus four jets without significant missing energy at hadron colliders. We find that via this unique channel, the heavy lepton can be searched for up to a mass of 200 GeV at the Tevatron with 8 fb^-1, and up to 450 (700) GeV at the LHC of 14 TeV C.M.energy with 10 (100) fb^-1. The signal rate at the 10 TeV LHC is reduced to 60-35% for a mass of 200-700 GeV. We also comment on how to distinguish this theory from other models with similar heavy leptons. Finally, we compare the production rates and angular distributions of heavy leptons in e+e- collisions for various models.
13106052
Large extra dimensions and dijet production in $\gamma \gamma$ collisions
We have studied dijet production in $\gamma \gamma$ collisions with a view to probing the physics of large extra dimensions. The exchange of virtual spin-2 Kaluza-Klein excitations is found to modify the dijet cross-section substantially from its Standard Model value and allows the effective string scale to be probed to values between 2.5 and 6.4 TeV in the unpolarised case. In the case where the photons are polarised, the limits are seen to improve by roughly 20%. Dijet production in $\gamma \gamma$ collisions is thus shown to be a very effective probe of large extra dimensions.
13886879
Constraints on supersymmetric flavor changing parameters using B ---> PP decays
We study contributions of quark-squark-gluino interactions in Minimal Supersymmetric Standard Model (MSSM) to B->PP (PP =Kpi, pipi, KK) decays using QCD improved factorization method for the evaluation of the hadronic matrix elements and taking into account renormalization group running of the Wilson coefficients from SUSY scale (~ m_{\tilde q}) to the low energy scale (= m_b) applicable to B decays. Using the most recent experimental data we obtain constraints on flavor changing Supersymmetric (SUSY) parameters (\delta_{ij})_{LL, RR}. For \Delta S = -1 processes, b-> s gamma is usually considered to give the strongest limits. We, however, find that in some part of the parameter space B-> Kpi processes give stronger bounds. Implications for B^0_s -\bar B^0_s mixing is discussed. We also study cons traints obtained from \Delta S = 0 processes B-> pipi, KK, rho gamma and B_d -\bar B_d mixing. In this case, in a large part of the parameter space B_d - \bar B_d provides the best bound, but B-> K^- K^0, rho gamma can still give interesting constraints in a complementary region of the parameter space.