International Journal of Modern Physics A

In this paper, we consider the case where electrons, magnetic monopoles and dyons become massless. Here, we consider the supersymmetric Yang–Mills (SYM) theories with classical gauge groups with a rank r, SU(r+1), SO(2r), Sp(2r) and SO(2r+1) which are studied by Riemann surfaces called Seiberg–Witten curves. We discuss physical singularity associated with massless particles, which can be studied by geometric singularity of vanishing 1-cycles in Riemann surfaces in hyperelliptic form. We pay particular attention to the cases where mutually nonlocal states become massless (Argyres–Douglas theories), which corresponds to Riemann surfaces degenerating into cusps. We discuss nontrivial topology on the moduli space of the theory, which is reflected as monodromy associated to vanishing 1-cycles. We observe how dyon charges get changed as we move around and through singularity in moduli space.

The Large Hadron Collider experiment has successfully completed data taking at center-of-mass energy 7 TeV in 2011 and very recently for 8 TeV. Measurements of cross-sections predicted by the standard model were the main tasks in the beginning. The inclusive jet cross-section and dijet mass measurement are already done at 7 TeV energy by Compact Muon Solenoid (CMS) detector with integrated luminosity 5 fb^-1. In these measurement, one needs to understand and measure precisely the kinematic properties of jets which involve many theoretical and experimental issues. The goal of this paper is to discuss all these issues including jet measurements in CMS and subsequently review the inclusive jet cross-section and dijet mass measurement in CMS at 7 TeV with integrated luminosity 5 fb^-1. The measurements, after unfolding the data, are also compared with the next-to-leading-order theory predictions, corrected for the nonperturbative effects, for five different sets of parton distribution functions. It is observed that the measurements, for both cases, agree with the theory prediction within ~8–10% depending on transverse momentum (p_T) and dijet invariant mass (M_jj) of jets.

Using soft-collinear effective theory, the leading-log radiative electroweak corrections are written in a closed and analytical form for the hadronic cross-section of Higgs production through vector boson fusion, qq → qqH, one of the most promising channels for studying the Higgs boson at Large Hadron Collider (LHC). The simple leading-log resummation is compared with a full next-to-leading-log calculation, and its accuracy is found to be of order 1% up to 10 TeV, i.e. better than the accuracy of parton distribution functions. Corrections are found to be larger than predicted by one-loop fixed-order approximations at LHC energies. The method provides a simple way of incorporating the electroweak corrections in software packages, improving the accuracy of simulations.

A forward amplitude analysis on pp and elastic scattering above 5 GeV is presented. The dataset includes the recent high-precision TOTEM measurements of the pp total and elastic (integrated) cross-sections at 7 TeV and 8 TeV. Following previous works, the leading high-energy contribution for the total cross-section (σ_tot) is parametrized as ln^γ(s/s_h), where γ and s_h are free real fit parameters. Singly-subtracted derivative dispersion relations are used to connect σ_tot and the rho parameter (ρ) in an analytical way. Different fit procedures are considered, including individual fits to σ_tot data, global fits to σ_tot and ρ data, constrained and unconstrained data reductions. The results favor a rise of the σ_tot faster than the log-squared bound by Froissart and Martin at the LHC energy region. The parametrization for σ_tot is extended to fit the elastic cross-section (σ_el) data with satisfactory results. The analysis indicates an asymptotic ratio σ_el/σ_tot consistent with 1/3 (as already obtained in a previous work). A critical discussion on the correlation, practical role and physical implications of the parameters γ and s_h is presented. The discussion confronts the 2002 prediction of σ_tot by the COMPETE Collaboration and the recent result by the Particle Data Group (2012 edition of the Review of Particle Physics). Some conjectures on possible implications of a fast rise of the proton–proton total cross-section at the highest energies are also presented.

Hattori–Itakura have recently derived the full Landau-level summation form for the photon vacuum polarization tensor in constant external magnetic fields at the one-loop level. The Landau-level summation form is essential when the photon momentum exceeds the threshold of the pair creation of charged particles in a magnetic field stronger than the squared mass of the charged particle. The tensor has three different form factors depending on the tensor direction with respect to the external magnetic field. The renormalization is nontrivial because these form factors are expressed in terms of double or triple summation forms. We give a numerical UV subtraction method which can be applied to numerically evaluate the form factors in constant external magnetic fields. We numerically investigate the photon vacuum polarization tensor in the form of the Landau-level summation and estimate the systematic errors coming from truncation of the Landau-level summation in a parameter region realized in heavy ion collision experiments. We find that the error is practically controllable at an O(10^-2) level for electrons and muons in strong magnetic fields expected in heavy ion collisions in the experimentally feasible kinematic parameter regions.

We report calculations of the gluon-induced Zg and Zgg productions in the Standard Model at the Large Hadron Collider (LHC) operating at both 7 TeV and 14 TeV collision energies. We present total cross-sections and differential distributions of the processes and compare them with the leading and next-to-leading order QCD pp → Z+1 jet, Z+2 jets results. Our results show that the gluon-induced Zg and Zgg productions contribute to pp → Z+1 jet, Z+2 jets at 1% level.

We consider Dyson–Schwinger Equations (DSEs) in the context of Connes–Kreimer renormalization Hopf algebra of Feynman diagrams and Connes–Marcolli universal Tannakian formalism. This study leads us to formulate a family of Picard–Fuchs equations and a category of Feynman motivic sheaves with respect to each combina torial DSE.