Searcharxiv⌕ Search

arXiv subjects

B. Ananthanarayan

Publications and source records attributed to B. Ananthanarayan.

At least 91 records · Page 5Linked to original sources
arXiv2008

Constraining the low energy pion electromagnetic form factor with space-like data

The pionic contribution to the g-2 of the muon involves a certain integral over the the modulus squared of F_π(t), the pion electromagnetic form factor. We extend techniques that use cut-plane analyticity properties of F_π(t) in order to account for present day estimates of the pionic contribution and experimental information at a finite number of points in the space-like region. Using data from several experiments over a large kinematic range for |t|, we find bounds on the expansion coefficients of F_π(t), sub-leading to the charge radius. The value of one of these coefficients in chiral perturbation theory respects these bounds. Furthermore, we present a sensitivity analysis to the inputs. A brief comparison with results in the literature that use observables other than the g-2 and timelike data is presented.

hep-ph↗
arXiv2007

Research News -- Quantum Mechanical Entanglement and Tests of CPT Theorem with Neutral Mesons at e+ e- Colliders

We review the recent confirmation of quantum entanglement in e+ e- collisions at the BELLE experiment at KEK-B in Japan with neutral B- mesons, and at the KLOE experiment at the DAFNE in Italy with neutral K- mesons. Such effects in the latter system seen already in proton-antiproton collisions by the CPLEAR experiment are also reviewed for purposes of comparison. In addition, the KLOE experiment provides new tests of the CPT theorem and are briefly discussed.

physics.pop-ph↗
arXiv2007

Sparticle Mass Spectrum in Grand Unified Theories

We carry out a detailed analysis of sparticle mass spectrum in supersymmetric grand unified theories. We consider the spectroscopy of the squarks and sleptons in SU(5) and SO(10) grand unified theories, and show how the underlying supersymmetry breaking parameters of these theories can be determined from a measurement of different sparticle masses. This analysis is done analytically by integrating the one-loop renormalization group equations with appropriate boundary conditions implied by the underlying grand unified gauge group. We also consider the impact of non-universal gaugino masses on the sparticle spectrum, especially the neutralino and chargino masses which arise in supersymmetric grand unified theories with non-minimal gauge kinetic function. In particular, we study the interrelationships between the squark and slepton masses which arise in grand unified theories at the one-loop level, which can be used to distinguish between the different underlying gauge groups and their breaking pattern to the Standard Model gauge group. We also comment on the corrections that can affect these one-loop results.

hep-ph↗
arXiv2007

Puzzles of excited charm meson masses

We attempt a comprehensive analysis of the low lying charm meson states which present several puzzles, including the poor determination of masses of several non-strange excited mesons. We use the well-determined masses of the ground states and the strange first excited states to `predict' the mass of the non-strange first excited state in the framework of heavy hadron chiral perturbation theory, an approach that is complementary to the well-known analysis of Mehen and Springer. This approach points to values for the masses of these states that are smaller than the experimental determinations. We provide a critical assessment of these mass measurements and point out the need for new experimental information.

hep-ph↗
arXiv2007

Research News -- Meson scattering at high precision

A fascinating new generation of experiments has determined certain meson scattering parameters at high precision. A confluence of highly sophisticated theory as well as new experimental ideas have led to this state of affairs, which sheds important light on the properties of the strong interactions. A brief review of the experiments and the theory is presented.

physics.pop-ph↗
arXiv2006

Probing space-time structure of new physics with polarized beams at the ILC

At the International Linear Collider large beam polarization of both the electron and positron beams will enhance the signature of physics due to interactions that are beyond the Standard Model. Here we review our recently obtained results on a general model independent method of determining for an arbitary one-particle inclusive state the space-time structure of such new physics through the beam polarization dependence and angular distribution of the final state particle.

hep-ph↗
arXiv2006

Operator Approach to Isospin Violation in Pion Photoproduction

Unambiguous isospin violation in the strong interaction sector is a key issue in low energy hadronic physics, both experimentally and theoretically. Bernstein has employed the Fermi-Watson theorem to demonstrate that pion photoproduction is a process where isospin violation in the pi N system can be revealed, an approach we review here. Here we propose a general operator approach to the phenomenon in pion photoproduction, thereby providing an analogue for the framework that was proposed for pi N scattering by Kaufmann and Gibbs. The resulting set of amplitudes could form the basis for determining the multipole amplitudes for photoproduction. Thus, the so resulting phase shift determination from photoproduction can then be used via the Fermi-Watson theorem to resolve discrepancies in pi N phase shift analyses. We point out that casting effective Lagrangian results in terms of our framework would be beneficial. The upcoming polarization experiments are an ideal setting to test our approach, and also to constrain better the isotensor currents which strictly are not forbidden.

hep-ph↗
arXiv2006

Space-time structure of new physics with polarized beams at the linear collider

We approach the issue of the discovery of new physics at high energies associated with the proposed International Linear Collider in the presence of longitudinal as well as transverse electron and positron beam polarization. We determine the beam polarization dependence and the angular distribution of a particle of arbitrary spin in a one-particle inclusive final state produced in e+ e- collisions through the interference of gamma or Z amplitude with the amplitude from new interactions having arbitrary space-time structure. We thus extend the results of Dass and Ross proposed at the time of the discovery of neutral currents, to beyond the standard model currents. We also extend the case of e+ e- annihilation in the s-channel to the production of bosons due to t- and u-channel processes. Our work provides an approach to model-independent determination of the space-time structure of beyond the standard model interactions. We briefly discuss applications of the framework to popular extensions of the standard model, and demonstrate that our framework is general enough to account for certain results in the minimal supersymmetric standard model.

hep-ph↗
arXiv2005

Comment on evidence for new interference phenomena in the decay D+ -> K- pi+ mu+ nu

The experimental determination of low energy pi K scattering phase shifts would assist in determining scattering lengths as well as low energy constants of chiral perturbation theory for which sum rules have been constructed. The FOCUS collaboration has presented evidence for interference pheomena from their analysis of D_l4 decays based on decay amplitudes suitable for a cascade decay D -> K* -> K pi. We point out that if the well-known full five body kinematics are taken into account, pi K scattering phases may be extracted. We also point out that other distributions considered in the context of K_l4 decays can be applied to charm meson decays to provide constraints on violation of |Delta I|=1/2 rule and T-violation.

hep-ph↗
arXiv2005

Fundamental particles and their interactions

In this article the current understanding of fundamental particles and their interactions is presented for the interested non-specialist, by adopting a semi-historical path. A discussion on the unresolved problems is also presented.

physics.pop-ph↗
arXiv2005

The role of polarized positrons and electrons in revealing fundamental interactions at the Linear Collider

The proposed International Linear Collider (ILC) is well-suited for discovering physics beyond the Standard Model and for precisely unraveling the structure of the underlying physics. The physics return can be maximized by the use of polarized beams. This report shows the paramount role of polarized beams and summarizes the benefits obtained from polarizing the positron beam, as well as the electron beam. The physics case for this option is illustrated explicitly by analyzing reference reactions in different physics scenarios. The results show that positron polarization, combined with the clean experimental environment provided by the linear collider, allows to improve strongly the potential of searches for new particles and the identification of their dynamics, which opens the road to resolve shortcomings of the Standard Model. The report also presents an overview of possible designs for polarizing both beams at the ILC, as well as for measuring their polarization.

hep-ph↗
arXiv2005

Probing SO(10) symmetry breaking patterns through sfermion mass relations

We consider supersymmetric SO(10) grand unification where the unified gauge group can break to the Standard Model gauge group through different chains. The breaking of SO(10) necessarily involves the reduction of the rank, and consequent generation of non-universal supersymmetry breaking scalar mass terms. We derive squark and slepton mass relations, taking into account these non-universal contributions to the sfermion masses, which can help distinguish between the different chains through which the SO(10) gauge group breaks to the Standard Model gauge group. We then study some implications of these non-universal supersymmetry breaking scalar masses for the low energy phenomenology.

hep-ph↗
arXiv2005

Scalar form factors of light mesons

The scalar radius of the pion plays an important role in CHPT, because it is related to one of the basic effective coupling constants, viz. the one which controls the quark mass dependence of F_pi at one loop. In a recent paper, Yndurain derives a {\it robust lower bound} for this radius, which disagrees with earlier determinations. We show that such a bound does not exist: the "derivation" relies on an incorrect claim. Moreover, we discuss the physics of the form factors associated with the operators \ubar u, \dbar d and \sbar s and show that their structure in the vicinity of the K \Kbar threshold is quite different. Finally, we draw attention to the fact that the new data on the slope of the scalar K_l3 form factor confirm a recent, remarkably sharp theoretical prediction.

hep-ph↗
arXiv2004

Transverse beam polarization and CP violation in e+ e- -> gamma Z with contact interactions

We consider the most general gauge-invariant, chirality-conserving contact interactions in the process e +e- -> gamma Z, of the type proposed Abraham and Lampe, in order to explore the possibility of CP violation at future linear colliders in the presence of polarized beams. We hereby extend recent work on CP violation due to anomalous triple-gauge boson vertices. We isolate combinations of couplings which are genuinely CP violating, pointing out which of these can only be studied with the use of transverse polarization. We place constraints on these couplings that could arise from suitably defined CP-odd asymmetries, considering realistic polarization (either longitudinal or transverse) of 80% and 60% for the electron and positron beams respectively, and with an integrated luminosity \int dt L of 500 fb^{-1} at a centre of mass energy of \sqrt{s}=500 GeV.

hep-ph↗
arXiv2004

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.

hep-ph↗