Summary of the Activities of the Working Group I on High Energy and Collider Physics
This is a summary of the projects undertaken by the Working Group I on High Energy Collider Physics at the Eighth Workshop on High Energy Physics Phenomenology (WHEPP8) held at the Indian Institute of Technology, Mumbai, January 5-16, 2004. The topics covered are (i) Higgs searches (ii) supersymmetry searches (iii) extra dimensions and (iv) linear collider.

title: Signals for gauge mediated supersymmetry breaking model at an e−e− collider
abstract: We study the pair-production and decay of right handed selectrons within a Gauge Mediated Supersymmetry Breaking Model in polarised e−e− interaction. Detailed analyses of the possible signals and backgrounds are performed for a few selected points in the parameter space. A judicious choice for polarisation of the initial electron beam helps eliminate almost the entire Standard Model background. We also show that phase space distributions can be used to distinguish such a supersummetry breaking scheme from the supergravity inspired models.

title: Constraining anomaly mediated supersymmetry breaking framework via ongoing muon g − 2 experiment at Brookhaven
abstract: The ongoing high precision E821 Brookhaven National Laboratory experiment on muon $g\ensuremath{-}2$ is promising to probe a theory involving supersymmetry. We have studied the constraints on the minimal anomaly mediated supersymmetry breaking (AMSB) model using the current data of muon $g\ensuremath{-}2$ from Brookhaven. A scenario of seeing no deviation from the standard model is also considered, within a $2\ensuremath{\sigma}$ limit of the combined error from the standard model result and the Brookhaven predicted uncertainty level. The resulting constraint is found to be complementary to what one obtains from $\stackrel{\ensuremath{\rightarrow}}{b}s+\ensuremath{\gamma}$ bounds within the AMSB scenario, since only a definite sign of $\ensuremath{\mu}$ is effectively probed via $\stackrel{\ensuremath{\rightarrow}}{b}s+\ensuremath{\gamma}.$ A few relevant generic features of the model are also described for disallowed regions of parameter space.

title: Collider Signatures for Heavy Lepton Triplet in Type I+III Seesaw
abstract: 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.

title: Invisible decays of Higgs and other mesons in models with singlet neutrinos in large extra dimensions
abstract: In light of current atmospheric neutrino oscillation data, we revisit the invisible decay of the standard model Higgs boson and other pseudoscalar mesons which can be enhanced because of large number of KK modes in models with right-handed singlet neutrinos in large extra dimensions. We find that the invisible decay rate of Higgs can be as large as H→b b decay rate only for a very restricted region of parameter space. This parameter space is even further restricted if one demands that the dimensionless neutrino Yukawa coupling λ is O (1). We have also studied the scenarios where singlet neutrino propagate in a sub-space, which lowers the string scale M ∗ and keeps neutrino Yukawa coupling O (1). We have also considered decays of other spin-0 mesons to ν ν and found the rates to be too small for measurement.

title: Study of single sneutrino production in association with fermion pairs at polarized photon colliders
abstract: We investigate single sneutrino production in the context of R-parity-violating supersymmetry at future ?? linear colliders. The sneutrino is produced in association with fermion pairs and it is shown that its decays into two further fermions will lead to a clean signal. We also discuss possible standard model backgrounds and the effects of beam polarization.

title: VOID ANALYSIS OF TARGET RESIDUES AT SPS ENERGY
abstract: This paper presents new data on void analysis of target residues in ultrarelativistic nucleus–nucleus interaction. The study reveals a set of interesting observations. Void probability shows a scaling behavior at high energy (32S–AgBr interactions at 200 A GeV) in both forward and backward hemisphere. Whereas such behavior is absent at low energy (16O–AgBr interactions at 60 A GeV) in backward hemisphere.

title: Evidence of scaling of void probability in nucleus-nucleus interactions at few GeV energy
abstract: The rapidity gap probability in the ${}^{24}\mathrm{M}\mathrm{g}\ensuremath{-}\mathrm{A}\mathrm{g}\mathrm{B}\mathrm{r}$ interaction at $4.5\mathrm{GeV}/c/\mathrm{nucleon}$ has been studied in detail. The data reveal scaling behavior of the void probability in the central rapidity domain which confirms the validity of the linked-pair approximation for the $N$-particle cumulant correlation functions. This scaling behavior appears to be similar to the void probability in the Perseus-Pisces supercluster region of galaxies.

title: MULTIPLICITY DISTRIBUTION AND MULTIPLICITY MOMENT OF BLACK AND GREY PARTICLES IN HIGH ENERGY NUCLEUS–NUCLEUS INTERACTIONS
abstract: 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.

title: Multifractal detrended fluctuation analysis of pseudorapidity and azimuthal distribution of pions emitted in high energy nuclear collisions
abstract: In this paper multifractal analysis of fluctuation pattern of pions emitted in 32S-AgBr and 16O-AgBr interactions at 200 GeV and 60 GeV, respectively, is performed in the framework of multifractal detrended fluctuation analysis (MFDFA). The pseudorapidity and azimuthal distributions exhibit multifractal scaling properties at both energies. The variation of multifractal width with energy is also studied. The study reveals a dependence of multifractal width on energy in pseudorapidity space while no such dependence is observed in azimuthal space.

title: Multidimensional intermittency study of target fragments at CERN SPS energies
abstract: An investigation on the presence of ring and jet-like structures is carried out in the angular emission of target-evaporated slow particles emitted in 16 O–Ag/Br interactions at 60 A GeV/c and 32 S–Ag/Br interactions at 200 A GeV/c. The nuclear emulsion technique was employed to collect the experimental data. We compared our experimental results with those obtained from Monte Carlo simulations. The analysis indicates the presence of ring and jet-like structures in the experimental data beyond the statistical noise. The presence of ring-like structure is fairly pronounced in 16 O–Ag/Br interactions compared to 32 S–Ag/Br interactions and jet-like structure is more distinct in 32 S. One dimensional (1d) intermittency for ring-like structures and two dimensional (2d) intermittency for jet-like structures are expected. The self-affine behavior of 2d scaled factorial moments (SFM) were investigated and the strength of 2d intermittency was determined. For each set of data, the 2d results were compared with the corresponding one-dimensional (1d) intermittency results. The strength in 2d is significantly greater than 1d for 32 S–Ag/Br interactions whereas for 16 O–Ag/Br interactions 1d is greater than 2d. This is also a sign of predominance of jets in 32 S–Ag/Br and the rings in 16 O–Ag/Br interactions.