Bounds on the possible evolution of the Gravitational Constant from Cosmological Type-Ia Supernovae

Recent high-redshift Type Ia supernovae results can be used to set new bounds on a possible variation of the gravitational constant $G$. If the local value of $G$ at the space-time location of distant supernovae is different, it would change both the kinetic energy release and the amount of $^{56}$Ni synthesized in the supernova outburst. Both effects are related to a change in the Chandrasekhar mass $M_{Ch} \propto G^{-3/2}$. In addition, the integrated variation of $G$ with time would also affect the cosmic evolution and therefore the luminosity distance relation. We show that the later effect in the magnitudes of Type Ia supernovae is typically several times smaller than the change produced by the corresponding variation of the Chandrasekhar mass. We investigate in a consistent way how a varying $G$ could modify the Hubble diagram of Type Ia supernovae and how these results can be used to set upper bounds to a hypothetical variation of $G$. We find G/G_0 \la 1.1 and G'/G \la 10^{-11} yr^{-1} at redshifts $z\simeq 0.5$. These new bounds extend the currently available constrains on the evolution of $G$ all the way from solar and stellar distances to typical scales of Gpc/Gyr, i.e. by more than 15 orders of magnitudes in time and distance.Comment: 9 pages, 4 figures, Phys. Rev. D. in pres

Measuring the metric: a parametrized post-Friedmanian approach to the cosmic dark energy problem

We argue for a ``parametrized post-Friedmanian'' approach to linear cosmology, where the history of expansion and perturbation growth is measured without assuming that the Einstein Field Equations hold. As an illustration, a model-independent analysis of 92 type Ia supernovae demonstrates that the curve giving the expansion history has the wrong shape to be explained without some form of dark energy or modified gravity. We discuss how upcoming lensing, galaxy clustering, cosmic microwave background and Lyman alpha forest observations can be combined to pursue this program, which generalizes the quest for a dark energy equation of state, and forecast the accuracy that the proposed SNAP satellite can attain.Comment: Replaced to match accepted PRD version. References and another example added, section III omitted since superceded by astro-ph/0207047. 11 PRD pages, 7 figs. Color figs and links at http://www.hep.upenn.edu/~max/gravity.html or from [email protected]

Search for jet extinction in the inclusive jet-pT spectrum from proton-proton collisions at s=8 TeV

Published by the American Physical Society under the terms of the Creative Commons Attribution 3.0 License. Further distribution of this work must maintain attribution to the author(s) and the published articles title, journal citation, and DOI.The first search at the LHC for the extinction of QCD jet production is presented, using data collected with the CMS detector corresponding to an integrated luminosity of 10.7  fb−1 of proton-proton collisions at a center-of-mass energy of 8 TeV. The extinction model studied in this analysis is motivated by the search for signatures of strong gravity at the TeV scale (terascale gravity) and assumes the existence of string couplings in the strong-coupling limit. In this limit, the string model predicts the suppression of all high-transverse-momentum standard model processes, including jet production, beyond a certain energy scale. To test this prediction, the measured transverse-momentum spectrum is compared to the theoretical prediction of the standard model. No significant deficit of events is found at high transverse momentum. A 95% confidence level lower limit of 3.3 TeV is set on the extinction mass scale

Performance of reconstruction and identification of τ leptons decaying to hadrons and vτ in pp collisions at √s=13 TeV

The algorithm developed by the CMS Collaboration to reconstruct and identify τ leptons produced in proton-proton collisions at √s=7 and 8 TeV, via their decays to hadrons and a neutrino, has been significantly improved. The changes include a revised reconstruction of π⁰ candidates, and improvements in multivariate discriminants to separate τ leptons from jets and electrons. The algorithm is extended to reconstruct τ leptons in highly Lorentz-boosted pair production, and in the high-level trigger. The performance of the algorithm is studied using proton-proton collisions recorded during 2016 at √s=13 TeV, corresponding to an integrated luminosity of 35.9 fb¯¹. The performance is evaluated in terms of the efficiency for a genuine τ lepton to pass the identification criteria and of the probabilities for jets, electrons, and muons to be misidentified as τ leptons. The results are found to be very close to those expected from Monte Carlo simulation

Measurement of angular parameters from the decay B⁰ → K⁎0^{⁎0} μ⁺ μ⁻ in proton–proton collisions at √s 8 TeV

Angular distributions of the decay B⁰  → K$^{⁎0}$ μ⁺ μ⁻ are studied using a sample of proton–proton collisions at √s=8TeV collected with the CMS detector at the LHC, corresponding to an integrated luminosity of 20.5fb⁻¹ . An angular analysis is performed to determine the P₁ and P$^{\u27}$₅ parameters, where the P$^{\u27}$₅ parameter is of particular interest because of recent measurements that indicate a potential discrepancy with the standard model predictions. Based on a sample of 1397 signal events, the P₁ and P$^{\u27}$₅ parameters are determined as a function of the dimuon invariant mass squared. The measurements are in agreement with predictions based on the standard model

Search for gauge-mediated supersymmetry in events with at least one photon and missing transverse momentum in pp collisions at √s = 13 TeV

A search for gauge-mediated supersymmetry (SUSY) in final states with photons and large missing transverse momentum is presented. The data sample of pp collisions at s=13TeV was collected with the CMS detector at the CERN LHC and corresponds to an integrated luminosity of 35.9 fb−1. Data are compared with models in which the lightest neutralino has bino- or wino-like components, resulting in decays to photons and gravitinos, where the gravitinos escape detection. The event selection is optimized for both electroweak (EWK) and strong production SUSY scenarios. The observed data are consistent with standard model predictions, and limits are set in the context of a general gauge mediation model in which gaugino masses up to 980 GeV are excluded at 95% confidence level. Gaugino masses below 780 and 950 GeV are excluded in two simplified models with EWK production of mass-degenerate charginos and neutralinos. Stringent limits are set on simplified models based on gluino and squark pair production, excluding gluino (squark) masses up to 2100 (1750) GeV depending on the assumptions made for the decay modes and intermediate particle masses. This analysis sets the highest mass limits to date in the studied EWK models, and in the considered strong production models when the mass difference between the gauginos and the squarks or gluinos is small