119163191
Search for a fermiophobic Higgs boson in pp collisions at $ \sqrt {s} = 7 $ TeV
A bstractCombined results are reported from searches for a fermiophobic Higgs boson in the γγ, WW, and ZZ decay modes in proton-proton collisions at $ \sqrt {s} = 7 $ TeV. The explored Higgs boson mass range is 110–300 GeV. The data sample corresponds to an integrated luminosity of 4.9–5.1 fb−1. A fermiophobic Higgs boson is excluded at 95% confidence level in the mass range 110–194 GeV, and at 99% confidence level in the mass ranges 110–124.5 GeV, 127–147.5 GeV, and 155–180 GeV.
117033883
Measurement of the single-top-quark t-channel cross section in pp collisions at $ \sqrt{s}=7 $ TeV
A bstractA measurement of the single-top-quark t-channel production cross section in pp collisions at $ \sqrt{s}=7 $ TeV with the CMS detector at the LHC is presented. Two different and complementary approaches have been followed. The first approach exploits the distributions of the pseudorapidity of the recoil jet and reconstructed top-quark mass using background estimates determined from control samples in data. The second approach is based on multivariate analysis techniques that probe the compatibility of the candidate events with the signal. Data have been collected for the muon and electron final states, corresponding to integrated luminosities of 1.17 and 1.56 fb−1, respectively. The single-top-quark production cross section in the t-channel is measured to be 67.2±6.1 pb, in agreement with the approximate next-to-next-to-leading-order standard model prediction. Using the standard model electroweak couplings, the CKM matrix element |Vtb| is measured to be 1.020 ± 0.046 (meas.) ± 0.017 (theor.).
18536190
Search for Excited Electrons in ep Collisions at HERA
A search for excited electrons is performed using the full e±p data sample collected by the H1 experiment at HERA, corresponding to a total luminosity of 475 pb−1. The electroweak decays of excited electrons e*→eγ, e*→eZ and e*→νW with subsequent hadronic or leptonic decays of the W and Z bosons are considered. No evidence for excited electron production is found. Mass dependent exclusion limits on e* production cross sections and on the ratio f/Λ of the coupling to the compositeness scale are derived within gauge mediated models. These limits extend the excluded region compared to previous excited electron searches. The e* production via contact interactions is also addressed for the first time in ep collisions.
36326465
Search for third-generation leptoquarks and scalar bottom quarks in pp collisions at $ \sqrt{s}=7\;TeV $
A bstractResults are presented from a search for third-generation leptoquarks and scalar bottom quarks in a sample of proton-proton collisions at $ \sqrt{s}=7\;TeV $ collected by the CMS experiment at the LHC, corresponding to an integrated luminosity of 4.7 fb−1. A scenario where the new particles are pair produced and each decays to a b quark plus a tau neutrino or neutralino is considered. The number of observed events is found to be in agreement with the standard model prediction. Upper limits are set at 95% confidence level on the production cross sections. Leptoquarks with masses below ~450 GeV are excluded. Upper limits in the mass plane of the scalar quark and neutralino are set such that scalar bottom quark masses up to 410 GeV are excluded for neutralino masses of 50 GeV.
54180669
DARK MATTER AND MASSIVE NEUTRINOS
119204233
Search for new physics in events with same-sign dileptons and b-tagged jets in pp collisions at $ \sqrt {s} = 7 $ TeV
A bstractA search for new physics is performed using isolated same-sign dileptons with at least two b-quark jets in the final state. Results are based on a 4.98 fb−1 sample of proton-proton collisions at a centre-of-mass energy of 7 TeV collected by the CMS detector. No excess above the standard model background is observed. Upper limits at 95% confidence level are set on the number of events from non-standard-model sources. These limits are used to set constraints on a number of new physics models. Information on acceptance and efficiencies are also provided so that the results can be used to confront additional models in an approximate way.
118126327
Periodic instantons in SU(2) Yang-Mills-Higgs theory
Abstract The properties of periodic instanton solutions of the classical SU (2) gauge theory with a Higgs doublet field are described analytically at low energies, and found numerically for all energies up to and beyond the sphaleron energy. Interesting new classes of bifurcating complex periodic instanton solutions to the Yang–Mills–Higgs equations are described.
2950123
LOW-MULTIPLICITY BURST SEARCH AT THE SUDBURY NEUTRINO OBSERVATORY
Results are reported from a search for low-multiplicity neutrino bursts in the Sudbury Neutrino Observatory. Such bursts could indicate the detection of a nearby core-collapse supernova explosion. The data were taken from Phase I (1999 November-2001 May), when the detector was filled with heavy water, and Phase II (2001 July-2003 August), when NaCl was added to the target. The search was a blind analysis in which the potential backgrounds were estimated and analysis cuts were developed to eliminate such backgrounds with 90% confidence before the data were examined. The search maintained a greater than 50% detection probability for standard supernovae occurring at a distance of up to 60 kpc for Phase I and up to 70 kpc for Phase II. No low-multiplicity bursts were observed during the data-taking period.
31197792
Nonparametric reconstruction of the dark energy equation of state from diverse data sets
The cause of the accelerated expansion of the Universe poses one of the most fundamental questions in physics today. In the absence of a compelling theory to explain the observations, a first task is to develop a robust phenomenological approach: If the acceleration is driven by some form of dark energy, then the phenomenology is determined by the form of the dark energy equation of state w(z) as a function of redshift. A major aim of ongoing and upcoming cosmological surveys is to measure w and its evolution at high accuracy. Since w(z) is not directly accessible to measurement, powerful reconstruction methods are needed to extract it reliably from observations. We have recently introduced a new reconstruction method for w(z) based on Gaussian process modeling. This method can capture nontrivial w(z) dependences and, most importantly, it yields controlled and unbiased error estimates. In this paper we extend the method to include a diverse set of measurements: baryon acoustic oscillations, cosmic microwave background measurements, and supernova data. We analyze currently available data sets and present the resulting constraints on w(z), finding that current observations are in very good agreement with a cosmological constant. In addition, we explore how well our methodmore » captures nontrivial behavior of w(z) by analyzing simulated data assuming high-quality observations from future surveys. We find that the baryon acoustic oscillation measurements by themselves already lead to remarkably good reconstruction results and that the combination of different high-quality probes allows us to reconstruct w(z) very reliably with small error bounds.« less
16633746
Capturing halos at high redshifts
We study the evolution of the mass function of dark matter halos in the concordance ΛCDM model at high redshift. We employ overlapping (multiple realization) numerical simulations to cover a wide range of halo masses, 107-1015 h-1 M☉, with redshift coverage beginning at z = 20. The Press-Schechter mass function is significantly discrepant from the simulation results at high redshifts. Of the more recently proposed mass functions, our results are in best agreement with those of Warren and coworkers. The statistics of the simulations—along with good control over systematics—allow for fits accurate to the level of 20% at all redshifts. We provide a concise discussion of various issues in defining and computing the halo mass function and how these are addressed in our simulations.
119181888
LSST Science Book, Version 2.0
A survey that can cover the sky in optical bands over wide fields to faint magnitudes with a fast cadence will enable many of the exciting science opportunities of the next decade. The Large Synoptic Survey Telescope (LSST) will have an effective aperture of 6.7 meters and an imaging camera with field of view of 9.6 deg^2, and will be devoted to a ten-year imaging survey over 20,000 deg^2 south of +15 deg. Each pointing will be imaged 2000 times with fifteen second exposures in six broad bands from 0.35 to 1.1 microns, to a total point-source depth of r~27.5. The LSST Science Book describes the basic parameters of the LSST hardware, software, and observing plans. The book discusses educational and outreach opportunities, then goes on to describe a broad range of science that LSST will revolutionize: mapping the inner and outer Solar System, stellar populations in the Milky Way and nearby galaxies, the structure of the Milky Way disk and halo and other objects in the Local Volume, transient and variable objects both at low and high redshift, and the properties of normal and active galaxies at low and high redshift. It then turns to far-field cosmological topics, exploring properties of supernovae to z~1, strong and weak lensing, the large-scale distribution of galaxies and baryon oscillations, and how these different probes may be combined to constrain cosmological models and the physics of dark energy.