Measurement of the reaction gamma*p->phi p in deep, inelastic e(+)p scattering at HERA

The production of phi mesons in the reaction e(+)p --> e(+)phi p (phi --> K+K-), for 7 phi p cross section rises strongly with W. This behaviour is similar to that previously found for the gamma*p --> rho(0)p cross section. This strong dependence cannot be explained by production through soft pomeron exchange, It is, however, consistent with perturbative QCD expectations, where it reflects the rise of the gluon momentum density in the proton at small x. The ratio of sigma(phi)/sigma(rho(0)), which has previously been determined by ZEUS to be 0.065 +/- 0.013 (stat.) in photoproduction at a mean W of 70 GeV, is measured to be 0.18 +/- 0.05 (stat.) +/- 0.03 (syst.) at a mean Q(2) of 12.3 GeV2 and mean W of approximate to 100 GeV and is thus approaching at large Q(2) the value of 2/9 predicted from the quark charges of the vector mesons and a flavour independent production mechanism

Search for R-parity-violating supersymmetry in a final state containing leptons and many jets with the ATLAS experiment using s√=13 TeV proton–proton collision data

A search for R-parity-violating supersymmetry in final states characterized by high jet multiplicity, at least one isolated light lepton and either zero or at least three b-tagged jets is presented. The search uses 139fb−1 of s√=13 TeV proton–proton collision data collected by the ATLAS experiment during Run 2 of the Large Hadron Collider. The results are interpreted in the context of R-parity-violating supersymmetry models that feature gluino production, top-squark production, or electroweakino production. The dominant sources of background are estimated using a data-driven model, based on observables at medium jet multiplicity, to predict the b-tagged jet multiplicity distribution at the higher jet multiplicities used in the search. Machine-learning techniques are used to reach sensitivity to electroweakino production, extending the data-driven background estimation to the shape of the machine-learning discriminant. No significant excess over the Standard Model expectation is observed and exclusion limits at the 95% confidence level are extracted, reaching as high as 2.4 TeV in gluino mass, 1.35 TeV in top-squark mass, and 320 (365) GeV in higgsino (wino) mass

Measurement of the reaction gamma*p->phi p in deep, inelastic e(+)p scattering at HERA

The production of phi mesons in the reaction e(+)p --> e(+)phi p (phi --> K+K-), for 7 phi p cross section rises strongly with W. This behaviour is similar to that previously found for the gamma*p --> rho(0)p cross section. This strong dependence cannot be explained by production through soft pomeron exchange, It is, however, consistent with perturbative QCD expectations, where it reflects the rise of the gluon momentum density in the proton at small x. The ratio of sigma(phi)/sigma(rho(0)), which has previously been determined by ZEUS to be 0.065 +/- 0.013 (stat.) in photoproduction at a mean W of 70 GeV, is measured to be 0.18 +/- 0.05 (stat.) +/- 0.03 (syst.) at a mean Q(2) of 12.3 GeV2 and mean W of approximate to 100 GeV and is thus approaching at large Q(2) the value of 2/9 predicted from the quark charges of the vector mesons and a flavour independent production mechanism

Moderfartøy i minevåpenet. En studie av hva dette konseptet vil bety for prosjekteringen av et fartøy

I denne oppgaven har jeg sett nærmere på hva prosjekteringen av en ny klasse minefartøy innebærer. Jeg har valgt å bruke PRINSIX modellen i den metodiske gjennomføringen. Ved å gjøre dette har jeg fått en realistisk tilnærming til prosjekteringsarbeidet. Jeg har gjennomført en konseptfase der jeg har klarlagt krav til kapasitet og funksjonalitet, i tillegg til å ha sett på hvordan nyttelasten, også kalt payload, til dette fartøyet vil kunne se ut i fremtiden. Med den konseptuelle løsningen som grunnlag startet jeg designarbeidet i definisjonsfasen. Her har jeg brukt en programvare som lar meg designe et fartøy, i tillegg til å hente ut de relevante dataene jeg trenger for å gjøre mine beregninger. Ved å bruke designspiralen har jeg hatt en metodisk tilnærming på designarbeidet, slik at jeg har vært i stand til å evaluere arbeidet mitt underveis, og dermed komme opp med konvergerende løsninger. Da dette er et svært omfattende arbeid, så vil mitt endelige designforslag ikke være fullstendig konvergerende, men heller et grunnlag for fremtidig arbeid. Siden problemstillingen spør om hva prosjekteringen av et slikt fartøy vil bety, er det naturlig at min konklusjon består av den lærdommen jeg har tilegnet meg i oppgaven: Et fartøy basert på moderskip-konseptet vil kreve en volumbasert prosjektering av fartøyet. Fartøyet må designes rundt payloaden, da hensikten med moderfartøyet er å fasilitere for at dette skal operere effektivt. Et slikt fartøy vil være betraktelig større enn dagens minefartøy. Innovative løsninger for deployering av payload, i tillegg til å beskytte dette for omgivelsene, vil være nødvendig for at dette skal være et levedyktig konsept. For å beskytte enheten må det vurderes om fartøyet skal ha tyngre våpen for selvforsvar, eller et designet operasjonsmønster med en eskorteenhet. Konseptuelt vil fartøyet ha en svært god kapasitet til minekrigføring, og prosjekteringen vil måtte se på antall enheter som skal brukes

Measurement of elastic omega photoproduction at HERA

Elastic photoproduction of vector mesons, gamma p --> Vp, has been extensively studied in fixed target experiments at centre-of-mass energies up to W approximate to 20 GeV. The production of rho(0), omega and phi is usually described in the framework of the vector meson dominance model (VDM) [1] and Regge theory [2]. The W dependence of the cross section can be parametrised in Regge theory by the sum of two terms, one due to Pomeron exchange and the other to Reggeon exchange, While the latter falls with W, the former is almost flat, Whereas rho(0) and phi production is predominantly due to Pomeron exchange at all energies, the energy behaviour of omega production investigated before HERA suggests a non-negligible contribution from Reggeon exchange. It is therefore of interest to analyse omega photoproduction at HERA, where Pomeron exchange should dominate. More specifically, it is important to establish if the features typical of elastic rho(0) and phi vector meson production are also observed in omega photoproduction at high energy. Among these features are the weak dependence of the elastic cross section on W, the exponential shape of the differential cross section in t, where t is the squared four momentum transferred at the proton vertex, and the observation that the vector meson retains the helicity of the photon (s-channel helicity conservation, SCHC), In addition, a comparison of the photoproduction cross sections of the light vector mesons rho(0) [3, 4], omega and phi [5] at HERA energies allows another check of their diffractive production mechanism. This paper reports a measurement of the photoproduction of omega mesons using the reaction ep --> e omega p with the ZEUS detector at HERA. The omega meson is observed via its decay into pi(+)pi(-)pi(0)(pi(0) --> gamma gamma) in the kinematic range 70 < W < 90 GeV and p(T)(2) < 0.6 GeV2, where p(T) is the transverse momentum of the omega with respect to the beam axis. For these events the scattered positron was not observed in the detector, thereby restricting the photon virtuality Q(2) to values smaller than 4 GeV2, with a median Q(2) of about 10(-4) GeV2

Measurement of the cross-section for the reaction gamme-P-]J/PSI-P with the ZEUS detector at HERA

This paper reports the cross section measurements for the process ep --> e J/psi p for Q(2) < 4 GeV2 at root s = 296 GeV, based on an integrated luminosity of about 0.5 pb(-1), using the ZEUS detector. The J/psi was detected in its e(+)e(-) and mu(+)mu(-) decay modes. The photoproduction cross section was measured to be 52(-12)(+7) +/- 10 nb at an average gamma p centre of mass energy of 67 GeV and 71(-20)(+13) +/- 12 nb at 114 GeV. The significant rise of the cross section compared to lower energy measurements is not in agreement with VDM models, but can be described by QCD inspired models if a rise in the gluon momentum density at low x in the proton is assumed

Measurement of elastic phi photoproduction at HERA

The production of phi mesons in the reaction e(+)p --> e(+)phi p (phi --> K+K-) at a median Q(2) of 10(-4) GeV2 has been studied with the ZEUS detector at HERA. The differential phi photoproduction cross section d sigma/dt has an exponential shape and has been determined in the kinematic range 0.1 phi p) = 0.96+/-0.19(-0.18)(+0.21) mu b has been obtained by extrapolating to t = 0. When compared to lower energy data, the results show a weak energy dependence of both sigma(gamma-->phi p) and the slope of the t distribution. The phi decay angular distributions are consistent with s-channel helicity conservation. From lower energies to HERA energies, the features of phi photoproduction are compatible with those of a soft diffractive process

MEASUREMENT OF MULTIPLICITY AND MOMENTUM SPECTRA IN THE CURRENT FRAGMENTATION REGION OF THE BREIT FRAME AT HERA

Charged particle production has been measured in Deep Inelastic Scattering (DIS) events using the ZEUS detector over a large range of Q(2) from 10 to 1280 GeV2 The evolution with Q of the charged multiplicity and scaled momentum has been investigated in the current fragmentation region of the Breit frame. The data are used to study QCD coherence effects in DIS and are compared with corresponding e(+)e(-) data in order to test the universality of quark fragmentation