Working group report: Physics at the Large Hadron Collider
This is a summary of the activities of the Physics at the LHC working group in the XIth Workshop on High Energy Physics Phenomenology (WHEPP-XI) held at the Physical Research Laboratory, Ahmedabad, India in January 2010. We discuss the activities of each sub-working group on physics issues at colliders such as Tevatron and Large Hadron Collider (LHC). The main issues discussed involve (1) results on W mass measurement and associated QCD uncertainties, (2) an attempt to understand the asymmetry measured at Tevatron in the top quark production, and (3) phenomenology of warped space dimension model.

title: Probing non-universal gaugino masses via Higgs boson production under SUSY cascades at the LHC: a detailed study
abstract: Cascade decays of Supersymmetric (SUSY) particles are likely to be prolific sources of Higgs bosons at the Large Hadron Collider (LHC). In this work, we explore, with the help of detailed simulation, the role of non-universal gaugino masses in the production of the Higgs bosons under SUSY cascades. The analysis is carried out by choosing an appropriate set of benchmark points with non-universal gaugino masses in the relevant SUSY parameter space and then contrasting the resulting observations with the corresponding cases having universal relationship among the same. It is shown that even of data at an early phase of the LHC-run with 10 fb−1 one would be able to see, under favourable situations, the imprint of non-universal gaugino masses by reconstructing various Higgs boson resonances and comparing their rates. With increased accumulated luminosities, the indications would naturally become distinct over a larger region of the parameter space.

title: Unusual Higgs boson signal in R-parity violating nonminimal supersymmetric models at the LHC
abstract: We predict an unconventional background free signal of the Higgs boson in $R$-parity violating nonminimal supersymmetric models at the Large Hadron Collider (LHC). The signal comprises dilepton plus four hadronic jets and two large displaced vertices. The displaced leptons and jets are coming from the decay of the lightest supersymmetric particle (LSP), which is predominantly a gauge-singlet neutrino. A pair of such LSPs can couple to a Higgs boson, created via gluon fusion. We have analyzed two cases - one corresponding to the tree-level Higgs boson mass and another with the one-loop corrected mass of the Higgs boson. A reliable Higgs mass reconstruction using this signal can lead to discovery at the LHC with center-of-mass energy $\sqrt{s}=14~\rm{TeV}$ and 5 fb$^{-1}$ of integrated luminosity $(\mathcal{L})$. Even at $\sqrt{s}=7~\rm{TeV}$ and $\mathcal{L}$ = 5 fb$^{-1}$, a reasonable number of events are expected. Besides, mass reconstruction of a gauge-singlet LSP can provide an estimate of the seesaw scale.

title: Displaced Higgs production in type III seesaw
abstract: We point out that the type III seesaw mechanism introducing fermion triplets predicts peculiar Higgs boson signatures of displaced vertices with two b jets and one or two charged particles which can be cleanly identified. In a supersymmetric theory, the scalar partner of the fermion triplet contains a neutral dark matter candidate which is almost degenerate with its charged components. A Higgs boson can be produced together with such a dark matter triplet in the cascade decay chain of a strongly produced squark or gluino. When the next lightest supersymmetric particle (NLSP) is bino/wino-like, there appears a Higgs boson associated with two charged tracks of a charged lepton and a heavy charged scalar at a displacement larger than about 1 mm. The corresponding production cross-section is about 0.5 fb for the squark/gluino mass of 1 TeV. In the case of the stau NLSP, it decays mainly to a Higgs boson and a heavy charged scalar whose decay length is larger than 0.1 mm for the stau NLSP mixing with the left-handed stau smaller than 0.3. As this process can have a large cascade production ∼2 pb for the squark/gluino mass ∼1 TeV, one may be able to probe it at the early stage of the LHC experiment.

title: Signatures of gaugino mass non-universality in cascade Higgs production at the LHC
abstract: Supersymmetric cascades, involving charginos and neutralinos at various stages, contribute in a significant way to Higgs production at the LHC. We explore the nature of such cascades, completely relaxing the universality of the gaugino masses. It is found that the deviation from the scenario with universal gaugino masses would be reflected in the relative production rates for the lightest neutral Higgs and the charged Higgses.

title: Higgs signatures in inverse seesaw model at the LHC
abstract: A bstractIn the inverse seesaw mechanism where the spontaneously broken B-L symmetry induces tiny B-L violating Majorana masses for right-handed neutrinos, non-standard Higgs signatures can arise due to a possible Higgs doublet and singlet mixing and/or Higgs boson decays to a left- and right-handed neutrino. This leads to a remarkable feature of hadronically quiet di-lepton final states which can exhibit, in particular, lepton flavour violating signatures coming from flavour-dependent neutrino Yukawa couplings. In this process, one lepton coming from the right-handed decay could be soft enough can be missed by the trigger level cuts of CMS and ATLAS for the di-lepton plus missing energy signature. The prospects of such a signature are investigated for 8 TeV and 14 TeV center of mass energy of the LHC, taking the maximum value of the allowed neutrino Yukawa coupling and the right-handed neutrino mass of 100 GeV. A PYTHIA level simulation shows that the integrated luminosity of 10-20/fb and 1.6/fb for 8 TeV is required to observe the inclusive leptonic and lepton flavour violating signatures, respectively. For 14 TeV, the reach is more and a larger parameter space of the inverse seesaw model can be probed.

title: Noncommutative Geometry, Quantum Hall Effect and Berry Phase
abstract: Taking resort to Haldane's spherical geometry we can visualize fractional quantum Hall effect on the noncommutative manifold $M_4 \times Z_N$ with $N>2$ and odd. The discrete space leads to the deformation of symplectic structure of the continuous manifold such that the symplectic area is given by $\triangle p.\triangle q=2\pi m \hbar$ with $m$ an odd integer which is related to the Berry phase and the filling factor is given by $\frac{1}{m}$. We here argue that this is equivalent to the noncommutative field theory as prescribed by Susskind and Polychronakos which is characterized by area preserving diffeomorphism. The filling factor $\frac{1}{m}$ is determined from the change in chiral anomaly and hence the Berry phase as envisaged by the star product.

title: Possible pulsation of neutron stars and neutrino emission
abstract: In recent times, pulsars seem to be the most perplexing astronomical objects observed by astrophysicists. To in terpre t these objects, several theories have been put forward by different authors. GOLD (~) has proposed tha t a rota t ing neutron star with large magnet ic field can account for the observed pulsat ing period, if we assume tha t there is a hot spot on the surface of the s tar from which pulses are generated. However, i t is ha rd to unders tand how this hot spot remains exact ly in the same position for a considerable period of t ime. Optical radiat ion coming from the same spot on the s tar is also seen on Ear th once for each rotat ion, but there should be a t ime delay between the optical and radio pulses corresponding to the t ime i t takes for the p lasma to t ravel outward to the point where the synchrotron radiat ion takes place. For the pulsar ~ P 0532, this t ime delay should be about 5 ms. However, in a recent experiment , i t has been measured to be (1.42 ± 0.34)ms (3). The al ternat ive model for pulsars has been suggested by GIlCZBURG and ZAITS~V (8) who suggested tha t pulsat ing neutron stars can account for the pulsar phenomena. To account for the second period observed in some pulsars, they correlated the short period with pulsat ion and the long period with rotat ion. However, i t has been pointed out by different authors tha t a serious difficulty arises for the pulsat ing model, since no mechanism for maintaining pulsat ion is known to exist in the case of neutron stars except for free oscillation. Any free oscillation is subject to dissipation and i t is generally believed tha t the most impor tan t dissipation mechanism in a neutron star is the emission of gravi ta t ional waves. A radia l ly pulsat ing nonrotat ing neutron s tar cannot emit gravi ta t ional waves, and if rotat ion is taken into account, the t ime for dissipation becomes ext remely short. Recently BAGLX~ and HEYVA~.RTS (4) have considered the possibil i ty of pulsars as nonradial oscillators. These authors have shown tha t long.period pulsars do not dissipate appreciably their energy by gravi ta t ional radiat ion, bu t short-period pulsars seem to be damped too quickly.

title: Dilepton production phenomena in high energy hadronic collisions
abstract: Experiments over the last few years have given rise to a blizzard of new and interesting results with regard to the production of various dileptons in high energy hadronic collisions. An attempt has here been made on the basis of some new ideas about the structure of hadrons and thus on a newly proposed version of the multiple production model to explain some of the crucial features in connection with the various multiplicity--ratios, cross--section ratios and the average values of the transverse momenta of the produced dileptons. In the backdrop of the hadron--hadron and lepton--hadron collisions, the model for dilopton production proposed here has some degree of generality which is one of its main features.

title: The photon as a composite state of a neutrino-antineutrino pair

title: Spin system, gauge theory, and renormalization group equation
abstract: The gauge theoretical formulation of a spin system is studied here. It is pointed out that a quantum spin can be associated with a gauge bundle where the gauge group is SU(2). The Ising spin is obtained by breaking the group to U(1) coupled with a Z2 symmetry giving rise to a Z2 gauge theory in three dimension. The gauge structure of a spin system helps us to reformulate the block‐variable transformation in terms of a gauge transformation.