A Search for Dark Higgs Bosons

Recent astrophysical and terrestrial experiments have motivated the proposal of a dark sector with GeV-scale gauge boson force carriers and new Higgs bosons. We present a search for a dark Higgs boson using 516 fb-1 of data collected with the BABAR detector. We do not observe a significant signal and we set 90% confidence level upper limits on the product of the Standard Model-dark sector mixing angle and the dark sector coupling constant.Comment: 7 pages, 5 postscript figures, published version with improved plots for b/w printin

Search for New Physics with Jets and Missing Transverse Momentum in pp collisions at sqrt(s) = 7 TeV

A search for new physics is presented based on an event signature of at least three jets accompanied by large missing transverse momentum, using a data sample corresponding to an integrated luminosity of 36 inverse picobarns collected in proton--proton collisions at sqrt(s)=7 TeV with the CMS detector at the LHC. No excess of events is observed above the expected standard model backgrounds, which are all estimated from the data. Exclusion limits are presented for the constrained minimal supersymmetric extension of the standard model. Cross section limits are also presented using simplified models with new particles decaying to an undetected particle and one or two jets

X-ray emission from the Sombrero galaxy: discrete sources

We present a study of discrete X-ray sources in and around the bulge-dominated, massive Sa galaxy, Sombrero (M104), based on new and archival Chandra observations with a total exposure of ~200 ks. With a detection limit of L_X = 1E37 erg/s and a field of view covering a galactocentric radius of ~30 kpc (11.5 arcminute), 383 sources are detected. Cross-correlation with Spitler et al.'s catalogue of Sombrero globular clusters (GCs) identified from HST/ACS observations reveals 41 X-rays sources in GCs, presumably low-mass X-ray binaries (LMXBs). We quantify the differential luminosity functions (LFs) for both the detected GC and field LMXBs, whose power-low indices (~1.1 for the GC-LF and ~1.6 for field-LF) are consistent with previous studies for elliptical galaxies. With precise sky positions of the GCs without a detected X-ray source, we further quantify, through a fluctuation analysis, the GC LF at fainter luminosities down to 1E35 erg/s. The derived index rules out a faint-end slope flatter than 1.1 at a 2 sigma significance, contrary to recent findings in several elliptical galaxies and the bulge of M31. On the other hand, the 2-6 keV unresolved emission places a tight constraint on the field LF, implying a flattened index of ~1.0 below 1E37 erg/s. We also detect 101 sources in the halo of Sombrero. The presence of these sources cannot be interpreted as galactic LMXBs whose spatial distribution empirically follows the starlight. Their number is also higher than the expected number of cosmic AGNs (52+/-11 [1 sigma]) whose surface density is constrained by deep X-ray surveys. We suggest that either the cosmic X-ray background is unusually high in the direction of Sombrero, or a distinct population of X-ray sources is present in the halo of Sombrero.Comment: 11 figures, 5 tables, ApJ in pres

Search for three-jet resonances in pp Collisions at √s=7 TeV

This article is published Open Access at sciencedirect.com. It is distributed under the terms of the Creative Commons Attribution License 3.0.-- et al.Results are reported from a search for the production of three-jet resonances in pp collisions at a center-of-mass energy √s=7  TeV. The study uses the data sample collected by the CMS experiment at the LHC in 2011, corresponding to an integrated luminosity of 5.0fb -1. Events with high jet multiplicity and a large scalar sum of jet transverse momenta are analyzed for the presence of resonances in the three-jet invariant mass spectrum. No evidence for a narrow resonance is found in the data, and limits are set on the cross section for gluino pair production in an R-parity-violating supersymmetry model, for gluino masses greater than 280 GeV. Assuming a branching fraction for gluino decay into three jets of 100%, gluino masses below 460 GeV are excluded at 95% confidence level. These results significantly extend the range of previous limits. © 2012 CERN.European Commission; Federal Ministry of Science, Research and Economy (Austria); ); Agency for Innovation by Science and Technology (Belgium); Conselho Nacional de Desenvolvimento Científico e Tecnológico (Brasil); Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (Brasil); Fundação Carlos Chagas Filho de Amparo à Pesquisa do Estado do Rio de Janeiro; Fundação de Amparo à Pesquisa do Estado de São Paulo; Ministry of Science and Technology of the People's Republic of China; National Natural Science Foundation of China; Colciencias (Colombia); Ministry of Science, Education and Sports of the Republic of Croatia; Research Promotion Foundation (Cyprus); Centre National de la Recherche Scientifique (France); Bundesministerium für Bildung und Forschung (Deutschland); Deutsche Forschungsgemeinschaft; General Secretariat of Research and Technology (Greece); Helsinki Institute of Physics; National Office for Research and Technology (Hungary); Institute for Research in Fundamental Sciences (Iran); Science Foundation Ireland; Istituto Nazionale di Fisica Nucleare (Italia); Compagnia di San Paolo (Italia); National Research Foundation of Korea; Centro de Investigación y de Estudios Avanzados del Instituto Politécnico Nacional (México); Consejo Nacional de Ciencia y Tecnología (México); Secretaría de Educación Pública (México); Universidad Autónoma de San Luis Potosí; Ministry of Science and Innovation (New Zealand); Pakistan Atomic Energy Commission; National Science Center (Poland); Fundação para a Ciência e a Tecnologia (Portugal); Joint Institute for Nuclear Research (Russia); Russian Foundation for Basic Research; Ministry of Education, Science and Technological Development (Serbia); Ministerio de Ciencia e Innovación (España); Swiss National Science Foundation.Peer Reviewe

Measurement of the t-channel single top quark production cross section in pp collisions at √s =7 TeV

Peer reviewe

Nietzsches gelijk: Waarom wijsheid achteraf onbillijk is

A search is performed for a massive new vector-like quark T, with charge 2/3, that is pair produced together with its antiparticle in proton-proton collisions. The data were collected by the CMS experiment at the Large Hadron Collider in 2012 at sqrt(s) = 8 TeV and correspond to an integrated luminosity of 19.5 inverse femtobarns. The T quark is assumed to decay into three different final states, bW, tZ, and tH. The search is carried out using events with at least one isolated lepton. No deviations from standard model expectations are observed, and lower limits are set on the T quark mass at 95% confidence level. The lower limit lies between 687 and 782 GeV for all possible values of the branching fractions into the three different final states assuming strong production. These limits are the most stringent constraints to date on the existence of such a quark

B0 meson decays to rho0 K*0, f0 K*0, and rho-K*+, including higher K* resonances

We present branching fraction measurements for the decays B0 -> rho0 K*0, B0 -> f0 K*0, and B0 -> rho- K*+, where K* is an S-wave (K pi)_0* or a K*(892) meson; we also measure B0 -> f0 K_2*(1430)^0. For the K*(892) channels, we report measurements of longitudinal polarization fractions (for rho final states) and direct CP-violation asymmetries. These results are obtained from a sample of (471.0 +/- 2.8) x 10^6 BBbar pairs collected with the BaBar detector at the PEP-II asymmetric-energy e+ e- collider at the SLAC National Accelerator Laboratory. We observe rho0 K*(892)^0, rho0 (K pi)_0^{*0}, f0 K*(892)^0, and rho- K*(892)+ with greater than 5 sigma significance, including systematics. We report first evidence for f0 (K pi)_0^{*0} and f0 K_2*(1430)^0, and place an upper limit on rho- (K pi)_0^{*+}. Our results in the K*(892) channels are consistent with no direct CP-violation.Comment: 17 pages, 6 postscript figures, submitted to Phys. Rev.

Strange Particle Production in pp Collisions at sqrt(s) = 0.9 and 7 TeV

Peer reviewe

Search for pair production of second-generation scalar leptoquarks in pp collisions at √s=7 TeV

This is the pre-print version of the Published Article which can be accessed from the link below.A search for pair production of second-generation scalar leptoquarks in the final state with two muons and two jets is performed using proton-proton collision data at √s=7  TeV collected by the CMS detector at the LHC. The data sample used corresponds to an integrated luminosity of 34  pb-1. The number of observed events is in good agreement with the predictions from the standard model processes. An upper limit is set on the second-generation leptoquark cross section times β2 as a function of the leptoquark mass, and leptoquarks with masses below 394 GeV are excluded at a 95% confidence level for β=1, where β is the leptoquark branching fraction into a muon and a quark. These limits are the most stringent to date

Search for large extra dimensions in the diphoton final state at the Large Hadron Collider

This is the pre-print version of the Published Article, which can be accessed from the link below - Copyright @ 2011 Springer VerlagA search for large extra spatial dimensions via virtual-graviton exchange in the diphoton channel has been carried out with the CMS detector at the LHC. No excess of events above the standard model expectations is found using a data sample collected in proton-proton collisions at Ös = 7s=7TeV and corresponding to an integrated luminosity of 36 pb− 1. New lower limits on the effective Planck scale in the range of 1.6–2.3TeV at the 95% confidence level are set, providing the most restrictive bounds to date on models with more than two large extra dimensions