A strong signal for double parton (DP) scattering is observed in a 16 pb(-1) sample of <(p)over bar p> --> gamma/pi(0) + 3 jets + X data from the CDF experiment at the Fermilab Tevatron. In DP events, two separate hard scatterings take place in a single <(p)over bar p> collision. We isolate a large sample of data (similar to 14 000 events) of which 53% are found to be DP. The process-independent parameter of double parton scattering, sigma(eff), is obtained without reference to theoretical calculations by comparing observed DP events to events with hard scatterings in separate <(p)over bar p> collisions. The result sigma(eff) = (14.5 +/- 1.7(-2.3)(+1.7)) mb represents a significant improvement over previous measurements, and is used to constrain simple models of parton spatial density. The Feynman x dependence of sigma(eff) is investigated and none is apparent. Further, no evidence is found for kinematic correlations between the two scatterings in DP events

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Search for the standard model Higgs boson produced in association with a W or a Z boson and decaying to bottom quarksThe CMS Collaboration * Abstract A search for the standard model Higgs boson (H) decaying to bb when produced in association with a weak vector boson (V) is reported for the following channels: W(µν)H, W(eν)H, W(τν)H, Z(µµ)H, Z(ee)H, and Z(νν)H. The search is performed in data samples corresponding to integrated luminosities of up to 5.1 fb −1 at √ s = 7 TeV and up to 18.9 fb −1 at √ s = 8 TeV, recorded by the CMS experiment at the LHC. An excess of events is observed above the expected background with a local significance of 2.1 standard deviations for a Higgs boson mass of 125 GeV, consistent with the expectation from the production of the standard model Higgs boson. The signal strength corresponding to this excess, relative to that of the standard model Higgs boson, is 1.0 ± 0.5.Published in Physical Review D as 2 Detector and simulated samples signal region. These regions also test the accuracy of the modeling of kinematic distributions in the simulated samples.Upper limits at the 95% CL on the pp → VH production cross section times the H → bb branching fraction are obtained for Higgs boson masses in the 110-135 GeV range. These limits are extracted by fitting the shape of the output distribution of a boosted-decision-tree (BDT) discriminant [14,15]. The results of the fitting procedure allow to evaluate the presence of a Higgs boson signal over the expectation from the background components. The significance of any excess of events, and the corresponding event yield, is compared with the expectation from a SM Higgs boson signal. Detector and simulated samplesA detailed description of the CMS detector can be found elsewhere [16]. The momenta of charged particles are measured using a silicon pixel and strip tracker that covers the pseudorapidity range |η| < 2.5 and is immersed in a 3.8 T axial magnetic field. The pseudorapidity is defined as η = − ln[tan(θ/2)], where θ is the polar angle of the trajectory of a particle with respect to the direction of the counterclockwise proton beam. Surrounding the tracker are a crystal electromagnetic calorimeter (ECAL) and a brass/scintillator hadron calorimeter (HCAL), both used to measure particle energy deposits and consisting of a barrel assembly and two endcaps. The ECAL and HCAL extend to a pseudorapidity range of |η| < 3.0. A steel/quartzfiber Cherenkov forward detector extends the calorimetric coverage to |η| < 5.0. The outermost component of the CMS detector is the muon system, consisting of gas-ionization detectors placed in the steel return yoke of the magnet to measure the momenta of muons traversing through the detector. The two-level CMS trigger system selects events of interest for permanent storage. The first trigger level, composed of custom hardware processors, uses information from the calorimeters and muon detectors to select events in less than 3.2 µs. The high-level trigger software algorithms, executed on a farm of commercial processor...

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.