An experiment to search for light sterile neutrinos is conducted at a reactor with a thermal power of 2.8 GW located at the Hanbit nuclear power complex. The search is done with a detector consisting of a ton of Gd-loaded liquid scintillator in a tendon gallery approximately 24 m from the reactor core. The measured antineutrino event rate is 1976 per day with a signal to background ratio of about 22. The shape of the antineutrino energy spectrum obtained from the eight-month data-taking period is compared with a hypothesis of oscillations due to activesterile antineutrino mixing. No strong evidence of 3+1 neutrino oscillation is found. An excess around the 5 MeV prompt energy range is observed as seen in existing longer-baseline experiments. The mixing parameter sin 2 2θ14 is limited up to less than 0.1 for ∆m The mixing among three neutrinos has been well established by experiments performed in the past two decades since the discovery of neutrino oscillations [1][2][3]. Consistent measurements of the two mass differences and the three mixing angles of the standard, three-neutrino mixing model have been reported by oscillation experiments using atmospheric, solar, reactor, and accelerator neutrinos [4]. Nevertheless, the mass hierarchy, the mass of the lightest neutrino, the Dirac or Majorana nature of the neutrino, and the CP phase are yet to be determined [5].Even though the number of active light neutrinos is limited to three by Z boson decay-width measurements [6], it is still possible to have additional neutrinos if they are sterile. Sterile neutrinos can be identified by the occurrence of activesterile neutrino oscillations. A hint for this is the LSND experiment's report of an observation ofν µ →ν e mixing with a frequency corresponding to a mass-squared difference larger than 0.01 eV 2 [7]. Results from the MiniBooNE's test of the LSND signal are, however, inconclusive [8].In addition to the LSND result, there are two other anomalies that could possibly be signs of active-sterile neutrino oscillations. An apparent ν e disappearance over a baseline of a few meters in the GALLEX and SAGE gallium experiments exposed to radioactive sources was reported [9]; the ratio of the numbers of measured and predicted events is 0.88 ± 0.05. A number of short-baseline reactor antineutrino experiments established limits on the presence of neutrino oscillations with eV mass differences by shape analyses of the measured neutrino energy spectra. Among those experiments, the Bugey experimental limits on sterile neutrinos are the most stringent [10]. Mueller et al. [11] found about a 6% deficit in reactor antineutrino event rates compared with the theoretical expectations for the short-baseline reactor experiments, which is the so-called "reactor antineutrino anomaly" (RAA). It can be interpreted as an active-sterile neutrino oscillation with three active neutrinos plus one or more sterile neutrinos, i.e., a 3 + n ν scenario [12,13], compatible with the LSND result. Recent reactor experiments that measured the θ 13 mixing an...

A search for supersymmetry with R-parity conservation in proton-proton collisions at a centre-of-mass energy of 7 TeV is presented. The data correspond to an integrated luminosity of 35 inverse picobarns collected by the CMS experiment at the LHC. The search is performed in events with jets and significant missing transverse energy, characteristic of the decays of heavy, pair-produced squarks and gluinos. The primary background, from standard model multijet production, is reduced by several orders of magnitude to a negligible level by the application of a set of robust kinematic requirements. With this selection, the data are consistent with the standard model backgrounds, namely t t-bar, W + jet and Z + jet production, which are estimated from data control samples. Limits are set on the parameters of the constrained minimal supersymmetric extension of the standard model. These limits extend those set previously by experiments at the Tevatron and LEP colliders

A search for neutral Higgs bosons in the minimal supersymmetric extension of the standard model (MSSM) decaying to tau-lepton pairs in pp collisions is performed, using events recorded by the CMS experiment at the LHC. The dataset corresponds to an integrated luminosity of 24.6 fb −1 , with 4.9 fb −1 at 7 TeV and 19.7 fb −1 at 8 TeV. To enhance the sensitivity to neutral MSSM Higgs bosons, the search includes the case where the Higgs boson is produced in association with a b-quark jet. No excess is observed in the tau-lepton-pair invariant mass spectrum. Exclusion limits are presented in the MSSM parameter space for different benchmark scenarios, m max h , m mod+ h , m mod− h , light-stop, lightstau, τ -phobic, and low-m H . Upper limits on the cross section times branching fraction for gluon fusion and b-quark associated Higgs boson production are also given. A Exclusion limits 23The CMS collaboration 37 IntroductionA broad variety of precision measurements have shown the overwhelming success of the standard model (SM) [1][2][3] of fundamental interactions, which includes an explanation for the origin of the mass of the weak force carriers, as well as for the quark and lepton masses. In the SM, this is achieved via the Brout-Englert-Higgs mechanism [4][5][6][7][8][9], which predicts the existence of a scalar boson, the Higgs boson. However, the Higgs boson mass in the SM is not protected against quadratically divergent quantum-loop corrections at high energy, known as the hierarchy problem. In the model of supersymmetry (SUSY) [10,11], which postulates a symmetry between the fundamental bosons and fermions, a cancellation of these divergences occurs naturally. The Higgs sector of the minimal supersymmetric extension of the standard model (MSSM) [12,13] The dominant neutral MSSM Higgs boson production mechanism is the gluon fusion process for small and moderate values of tan β. At large values of tan β b-quark associated production is the dominant contribution, due to the enhanced Higgs boson Yukawa coupling to b quarks. Figure 1 shows the leading-order diagrams for the gluon fusion and b-quark associated Higgs boson production, in the four-flavor and in the five-flavor scheme. In the region of large tan β the branching fraction to tau leptons is also enhanced, making the search for neutral MSSM Higgs bosons in the τ τ final state particularly interesting. This paper reports a search for neutral MSSM Higgs bosons in pp collisions at √ s = 7 TeV and 8 TeV in the τ τ decay channel. The data were recorded with the CMS detector [14] at the CERN LHC and correspond to an integrated luminosity of 24.6 fb −1 , with 4.9 fb −1 at 7 TeV and 19.7 fb −1 at 8 TeV. Five different τ τ signatures are studied, eτ h , µτ h , eµ, µµ, and τ h τ h , where τ h denotes a hadronically decaying τ . These results are an extension of previous searches by the The results are interpreted in the context of the MSSM with different benchmark scenarios described in section 1.1 and also in a model independent way, in terms of upper...

The results of comprehensive studies of missing transverse energy as measured by the CMS detector in pp collisions at a centre-of-mass energy of 7 TeV are presented. Three missing transverse energy reconstruction algorithms are deployed for various physics analyses. The scale and resolution for missing transverse energy are validated using vector boson and dijet events, and severe mismeasurements due to the detector are studied. We also parametrize the effects of multiple pp interactions within the same bunch crossings on the scale and resolution. A tool, called missing transverse energy significance, based on particle resolutions in each event is also presented.

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