Tata Institute of Fundamental Research

About: Tata Institute of Fundamental Research is a education organization based out in Mumbai, Maharashtra, India. It is known for research contribution in the topics: Magnetization & Large Hadron Collider. The organization has 7786 authors who have published 21742 publications receiving 622368 citations. The organization is also known as: TIFR.

A simulation-calibrated limit on the H i power spectrum from the GMRT Epoch of Reionization experiment

Abstract: The Giant Metrewave Radio Telescope Epoch of Reionization experiment is an ongoing effort to measure the power spectrum from neutral hydrogen at high redshift. We have previously reported an upper limit of (70 mK)^2 at wavenumbers of k ≈ 0.65 h Mpc^(−1) using a basic piecewise-linear foreground subtraction. In this paper, we explore the use of a singular value decomposition to remove foregrounds with fewer assumptions about the foreground structure. Using this method, we also quantify, for the first time, the signal loss due to the foreground filter and present new power spectra adjusted for this loss, providing a revised measurement of a 2σ upper limit at (248 mK)^2 for k = 0.50 h Mpc^(−1). While this revised limit is larger than previously reported, we believe it to be more robust and still represents the best current constraint on reionization at z ≈ 8.6.

Search for supersymmetry at the LHC in events with jets and missing transverse energy

Abstract: A search for events with jets and missing transverse energy is performed in a data sample of pp collisions collected at sqrt(s) = 7 TeV by the CMS experiment at the LHC. The analyzed data sample corresponds to an integrated luminosity of 1.14 inverse femtobarns. In this search, a kinematic variable, alphaT, is used as the main discriminator between events with genuine and misreconstructed missing transverse energy. No excess of events over the standard model expectation is found. Exclusion limits in the parameter space of the constrained minimal supersymmetric extension of the standard model are set. In this model, squark masses below 1.1 TeV are excluded at 95% CL. Gluino masses below 1.1 TeV are also ruled out at 95% CL for values of the universal scalar mass parameter below 500 GeV.

Observation of a Near-Threshold ωJ/ψ Mass Enhancement in Exclusive B→KωJ/ψ Decays

Abstract: Reference EPFL-ARTICLE-154584doi:10.1103/PhysRevLett.94.182002View record in Web of Science Record created on 2010-11-05, modified on 2017-12-10

Ultraviolet Survey of CO and H2 in Diffuse Molecular Clouds: The Reflection of Two Photochemistry Regimes in Abundance Relationships

Abstract: We carried out a comprehensive far-UV survey of 12CO and H2 column densities along diffuse molecular Galactic sight lines. This sample includes new measurements of CO from HST spectra along 62 sight lines and new measurements of H2 from FUSE data along 58 sight lines. In addition, high-resolution optical data were obtained at the McDonald and European Southern Observatories, yielding new abundances for CH, CH+, and CN along 42 sight lines to aid in interpreting the CO results. These new sight lines were selected according to detectable amounts of CO in their spectra and provide information on both lower density (≤100 cm−3) and higher density diffuse clouds. A plot of -->log N(CO) versus -->log N(H2) shows that two power-law relationships are needed for a good fit of the entire sample, with a break located at -->log N(CO , cm −2) = 14.1 and -->log N(H2) = 20.4, corresponding to a change in production route for CO in higher density gas. Similar logarithmic plots among all five diatomic molecules reveal additional examples of dual slopes in the cases of CO versus CH (break at -->log N = 14.1, 13.0), CH+ versus H2 (13.1, 20.3), and CH+ versus CO (13.2, 14.1). We employ both analytical and numerical chemical schemes in order to derive details of the molecular environments. In the denser gas, where C2 and CN molecules also reside, reactions involving C+ and OH are the dominant factor leading to CO formation via equilibrium chemistry. In the low-density gas, where equilibrium chemistry studies have failed to reproduce the abundance of CH+, our numerical analysis shows that nonequilibrium chemistry must be employed for correctly predicting the abundances of both CH+ and CO.