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 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

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

Study of charged-current ep interactions at Q(2)&gt;200 GeV2 with the ZEUS detector at HERA

Deep inelastic charged-current reactions have been studied in e+p and e-p collisions at a center of mass energy of about 300GeV in the kinematic region Q2&gt;200GeV2 and x&gt;0.006 using the ZEUS detector at HERA. The integrated cross sections for Q2&gt;200GeV2 are found to be {Mathematical expression} and {Mathematical expression}. Differential cross sections have been measured as functions of the variables x, y and Q2. From the measured differential cross sections dσ/dQ2, the W boson mass is determined to be {Mathematical expression}. Measured jet rates and transverse energy profiles agree with model predictions. A search for charged-current interactions with a large rapidity gap yielded one candidate event, corresponding to a cross section of {Mathematical expression} © 1996 Springer-Verlag

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 the diffractive cross-section in deep inelastic scattering

Diffractive scattering of $\gamma^* p \to X + N$, where $N$ is either a proton or a nucleonic system with $M_N~<~4$~GeV has been measured in deep inelastic scattering (DIS) at HERA. The cross section was determined by a novel method as a function of the $\gamma^* p$ c.m. energy $W$ between 60 and 245~GeV and of the mass $M_X$ of the system $X$ up to 15~GeV at average $Q^2$ values of 14 and 31~GeV$^2$. The diffractive cross section $d\sigma^{diff} /dM_X$ is, within errors, found to rise linearly with $W$. Parameterizing the $W$ dependence by the form d\sigma^{diff}/dM_X \propto (W^2)^{(2\overline{\mbox{\alpha_{_{I\hspace{-0.2em}P}}}} -2)} the DIS data yield for the pomeron trajectory \overline{\mbox{\alpha_{_{I\hspace{-0.2em}P}}}} = 1.23 \pm 0.02(stat) \pm 0.04 (syst) averaged over $t$ in the measured kinematic range assuming the longitudinal photon contribution to be zero. This value for the pomeron trajectory is substantially larger than \overline{\mbox{\alpha_{_{I\hspace{-0.2em}P}}}} extracted from soft interactions. The value of \overline{\mbox{\alpha_{_{I\hspace{-0.2em}P}}}} measured in this analysis suggests that a substantial part of the diffractive DIS cross section originates from processes which can be described by perturbative QCD. From the measured diffractive cross sections the diffractive structure function of the proton F^{D(3)}_2(\beta,Q^2, \mbox{x_{_{I\hspace{-0.2em}P}}}) has been determined, where $\beta$ is the momentum fraction of the struck quark in the pomeron. The form F^{D(3)}_2 = constant \cdot (1/ \mbox{x_{_{I\hspace{-0.2em}P}}})^a gives a good fit to the data in all $\beta$ and $Q^2$ intervals with $a = 1.46 \pm 0.04 (stat) \pmComment: 45 pages, including 16 figure

Study of photon dissociation in diffractive photoproduction at HERA

Diffractive dissociation of quasi-real photons at a photon-proton centre of mass energy of W ≈ 200 GeV is studied with the ZEUS detector at HERA. The process under consideration is γp → XN, where X is the diffractively dissociated photon system of mass MX and N is either a proton or a nucleonic system with mass MN &lt; 2 GeV. The cross section for this process in the interval 3 &lt; MX &lt; 24 GeV relative to the total photoproduction cross section was measured to be σDpartial/σtot = 6.2 ± 0.2(stat) ± 1.4(syst)%. After extrapolating this result to the mass interval of mφ2 &lt; MX2 &lt; 0.05W2 and correcting it for proton dissociation, the fraction of the total cross section attributed to single diffractive photon dissociation, γp → Xp, is found to be σSD/σtot = 13.3 ± 0.5(stat) ± 3.6(syst)%. The mass spectrum of the dissociated photon system in the interval 8 &lt; MX &lt; 24 GeV can be described by the triple pomeron (IP IP IP) diagram with an effective pomeron intercept of αIP(0) = 1.12 ± 0.04(stat) ± 0.08(syst). The cross section for photon dissociation in the range 3 &lt; MX &lt; 8 GeV is significantly higher than that expected from the triple pomeron amplitude describing the region 8 &lt; MX &lt; 24 GeV. Assuming that this discrepancy is due to a pomeron-pomeron-reggeon (IP IP IR) term, its contribution to the diffractive cross section in the interval 3 &lt; MX &lt; 24 GeV is estimated to be fIP IP IR = 26 ± 3(stat) ± 12(syst)%. © Springer-Verlag 1997

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