Measurement of D+- and D0 production in deep inelastic scattering using a lifetime tag at HERA

The production of D-+/-- and D-0-mesons has been measured with the ZEUS detector at HERA using an integrated luminosity of 133.6 pb(-1). The measurements cover the kinematic range 5 < Q(2) < 1000 GeV2, 0.02 < y < 0.7, 1.5 < p(T)(D) < 15 GeV and |eta(D)| < 1.6. Combinatorial background to the D-meson signals is reduced by using the ZEUS microvertex detector to reconstruct displaced secondary vertices. Production cross sections are compared with the predictions of next-to-leading-order QCD, which is found to describe the data well. Measurements are extrapolated to the full kinematic phase space in order to obtain the open-charm contribution, F-2(c (c) over bar), to the proton structure function, F-2

The Electronics and Data Acquisition System of the DarkSide Dark Matter Search

It is generally inferred from astronomical measurements that Dark Matter (DM) comprises approximately 27\% of the energy-density of the universe. If DM is a subatomic particle, a possible candidate is a Weakly Interacting Massive Particle (WIMP), and the DarkSide-50 (DS) experiment is a direct search for evidence of WIMP-nuclear collisions. DS is located underground at the Laboratori Nazionali del Gran Sasso (LNGS) in Italy, and consists of three active, embedded components; an outer water veto (CTF), a liquid scintillator veto (LSV), and a liquid argon (LAr) time projection chamber (TPC). This paper describes the data acquisition and electronic systems of the DS detectors, designed to detect the residual ionization from such collisions

DarkSide-50, a background free experiment for dark matter searches

The existence of dark matter is inferred from gravitational effects, but its nature remains a deep mystery. One possibility, motivated by considerations in elementary particle physics, is that dark matter consists of elementary particles, such as the hypothesized Weakly Interacting Massive Particles (WIMPs), with mass ~ 100 GeV and cross-section ~ 10−47 cm2, that can be gravitationally trapped inside our galaxy and revealed by their scattering on nuclei. It should be possible to detect WIMPs directly, as the orbital motion of the WIMPs composing the dark matter halo pervading the galaxy should result in WIMP-nucleus collisions of sufficient energy to be observable in the laboratory. The DarkSide-50 experiment is a direct WIMP search using a Liquid Argon Time Projection Chamber (LAr-TPC) with an active mass of 50 kg with a high sensitivity and an ultra-low background detector

First Results from the DarkSide-50 Dark Matter Experiment at Laboratori Nazionali del Gran Sasso

We report the first results of DarkSide-50, a direct search for dark matter operating in the un- derground Laboratori Nazionali del Gran Sasso (LNGS) and searching for the rare nuclear recoils possibly induced by weakly interacting massive particles (WIMPs). The dark matter detector is a Liquid Argon Time Projection Chamber with a ( 46.4 0.7 ) kg active mass, operated inside a 30 t or- ganic liquid scintillator neutron veto, which is in turn installed at the center of a 1 kt water Cherenkov veto for the residual flux of cosmic rays. We report here the null results of a dark matter search for a ( 1422 67 ) kg d exposure with an atmospheric argon fill. This is the most sensitive dark matter search performed with an argon target, corresponding to a 90% CL upper limit on the WIMP-nucleon spin-independent cross section of 6.1 1

The Electronics and Data Acquisition System of the DarkSide Dark Matter Search

It is generally inferred from astronomical measurements th at Dark Matter (DM) comprises approximately 27% of the energy-dens ity of the universe. If DM is a subatomic particle, a possible candidate is a Weakl y Interacting Mas- sive Particle (WIMP), and the DarkSide-50 (DS) experiment i s a direct search for evidence of WIMP-nuclear collisions. DS is located undergr ound at the Laboratori Nazionali del Gran Sasso (LNGS) in Italy, and consists of thr ee active, embedded components; an outer water veto (CTF), a liquid scintillato r veto (LSV), and a liquid argon (LAr) time projection chamber (TPC). This pap er describes the data acquisition and electronic systems of the DS detectors , designed to detect the residual ionization from

Multi-Leptons with High Transverse Momentum at HERA

18 pages, 3 figures, revised version with small textual changesEvents with at least two high transverse momentum leptons (electrons or muons) are studied using the H1 and ZEUS detectors at HERA with an integrated luminosity of 0.94 fb^{-1}. The observed numbers of events are in general agreement with the Standard Model predictions. Seven di- and tri-lepton events are observed in e^+p collision data with a scalar sum of the lepton transverse momenta above 100 GeV while 1.94+-0.17 events are expected. Such events are not observed in e^-p collisions for which 1.19+-0.12 are predicted. Total visible and differential di-electron and di-muon photoproduction cross sections are extracted in a restricted phase space dominated by photon-photon collisions

Production of Excited Charm and Charm-Strange Mesons at HERA

The production of excited charm, D 1(2420)0 and D 2 * (2460)0, and charm-strange, D s1(2536)±, mesons in ep collisions was measured with the ZEUS detector at HERA using an integrated luminosity of 126 pb -1. Masses, widths and helicity parameters were determined. The measured yields were converted to the rates of c quarks hadronising as a given excited charm meson and to the ratios of the dominant D 2 * (2460)0 and D s1(2536) ± branching fractions. A search for the radially excited charm meson, D *(2640)±, was also performed. The results are compared with those measured previously and with theoretical expectations

Search for pair production of third-generation scalar leptoquarks and top squarks in proton-proton collisions at v root s=8 TeV

A search for pair production of third-generation scalar leptoquarks and supersymmetric top quark partners, top squarks, in final states involving tau leptons and bottom quarks is presented. The search uses events from a data sample of proton-proton collisions corresponding to an integrated luminosity of 19.7 fb(-1), collected with the CMS detector at the LHC with root s = 8 TeV. The number of observed events is found to be in agreement with the expected standard model background. Third-generation scalar leptoquarks with masses below 740 GeV are excluded at 95% confidence level, assuming a 100% branching fraction for the leptoquark decay to a tau lepton and a bottom quark. In addition, this mass limit applies directly to top squarks decaying via an R-parity violating coupling. lambda(') (333). The search also considers a similar signature from top squarks undergoing a chargino-mediated decay involving the Rparity violating coupling. lambda(')(3jk). Each top squark decays to a tau lepton, a bottom quark, and two light quarks. Top squarks in this model with masses below 580 GeV are excluded at 95% confidence level. The constraint on the leptoquark mass is the most stringent to date, and this is the first search for top squarks decaying via. lambda(')(3jk)

Koulutusluokitus : Koulutuskoodimuutokset vuonna 1989, Liite 3

A measurement of inclusive ZZ production cross section and constraints on anomalous triple gauge couplings in proton-proton collisions at $\sqrt{s}$ = 8 TeV are presented. A data sample, corresponding to an integrated luminosity of 19.6 inverse-femtobarns was collected with the CMS experiment at the LHC. The measurements are performed in the leptonic decay modes $ZZ \to lll'l'$, where $l = e, \mu$ and $l' = e, \mu, \tau$. The measured total cross section, $\sigma (pp \to ZZ) = 7.7 \pm 0.5 (stat.)^{+0.5}_{-0.4} (syst.) \pm 0.4 (theo.) \pm 0.2 (lum.) pb$ for both Z bosons produced in the mass range $m_Z$ within 60 and 120 GeV, is consistent with standard model predictions. Differential cross sections are measured and well described by the theoretical predictions. The invariant mass distribution of the four-lepton system is used to set limits on anomalous ZZZ and ZZ$\gamma$ couplings at the 95% confidence level: $f_4^Z$ in (-0.004,+0.004), $f_5^Z$ in (-0.005,+0.005), $f_4^\gamma$ in (-0.004,+0.004), and $f_5^\gamma$ in (-0.005,+0.005)