Publications (347)310.94 Total impact

Article: The CMS experiment at the CERN LHC
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ABSTRACT: The Compact Muon Solenoid (CMS) detector is described. The detector operates at the Large Hadron Collider (LHC) at CERN. It was conceived to study protonproton (and leadlead) collisions at a centreofmass energy of 14 TeV (5.5 TeV nucleonnucleon) and at luminosities up to 1034 cm−2 s−1 (1027 cm−2 s−1). At the core of the CMS detector sits a highmagneticfield and largebore superconducting solenoid surrounding an allsilicon pixel and strip tracker, a leadtungstate scintillatingcrystals electromagnetic calorimeter, and a brassscintillator sampling hadron calorimeter. The iron yoke of the fluxreturn is instrumented with four stations of muon detectors covering most of the 4π solid angle. Forward sampling calorimeters extend the pseudorapidity coverage to high values (η ≤ 5) assuring very good hermeticity. The overall dimensions of the CMS detector are a length of 21.6 m, a diameter of 14.6 m and a total weight of 12500 t.Journal of Instrumentation 08/2008; 3(08):S08004. · 1.53 Impact Factor 
Article: The CMS high level trigger
European Physical Journal C 06/2006; 46(3):605667. · 5.44 Impact Factor 
Article: The CMS High Level Trigger
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ABSTRACT: At the Large Hadron Collider at CERN the proton bunches cross at a rate of 40MHz. At the Compact Muon Solenoid experiment the original collision rate is reduced by a factor of O (1000) using a Level1 hardware trigger. A subsequent factor of O(1000) data reduction is obtained by a softwareimplemented High Level Trigger (HLT) selection that is executed on a multiprocessor farm. In this review we present in detail prototype CMS HLT physics selection algorithms, expected trigger rates and trigger performance in terms of both physics efficiency and timing.11/2005;  [Show abstract] [Hide abstract]
ABSTRACT: Deepinelastic e±p scattering at high squared momentum transfer Q2 up to 30 000 GeV2 is used to search for eq contact interactions associated to scales far beyond the Hera centre of mass energy. The neutral current cross section measurements dσ/dQ2, corresponding to integrated luminosities of 16.4 pb−1 of e−p data and 100.8 pb−1 of e+p data, are well described by the Standard Model and are analysed to set constraints on new phenomena. For conventional contact interactions lower limits are set on compositeness scales Λ ranging between 1.6–5.5 TeV. Couplings and masses of leptoquarks and squarks in Rparity violating supersymmetry are constrained to M/λ>0.3–1.4 TeV. A search for low scale quantum gravity effects in models with large extra dimensions provides limits on the effective Planck scale of MS>0.8 TeV. A form factor analysis yields a bound on the radius of light quarks of Rq<1.0×10−18 m.Physics Letters B 05/2003; 568:3547. · 6.02 Impact Factor  [Show abstract] [Hide abstract]
ABSTRACT: Results on diffractive photoproduction of psi(2S) mesons are presented using data collected between 1996 and 2000 with the H1 detector at the HERA ep collider. The data correspond to an integrated luminosity of 77 pb(1). The energy dependence of the diffractive psi(2S) cross section is found to be similar to or possibly somewhat steeper than that for J/psi mesons. The dependences of the elastic and proton dissociative psi(2S) photoproduction cross sections on the squared momentum transfer t at the proton vertex are measured. The tdependence of the elastic channel, parametrised as e(bt), yields b(el)(psi(2S)) = (4.31 +/ 0.57 +/ 0.46) GeV2, compatible with that of the J/psi. For the proton dissociative channel the result b(pd)(psi(2S)) = (0.59 +/ 0.13 +/ 0.12) GeV2 is 2.3 standard deviations smaller than that measured for the J/psi. With proper account of the individual wavefunctions theoretical predictions based on perturbative QCD are found to describe the measurements well. (C) 2002 Elsevier Science B.V. All rights reserved.Physics Letters B 09/2002; 541:251264. · 6.02 Impact Factor  [Show abstract] [Hide abstract]
ABSTRACT: Dijet events in photonproton collisions in which there is a large pseudorapidity separation, Deltaeta > 2.5 between the two highest ET jets are studied with the H1 detector at HERA. The inclusive dijet cross sections are measured as functions of the longitudinal momentum fractions of the proton and photon which participate in the production of the jets, x(p)(jets) and x(gamma)(jets) respectively, Deltaeta, the pseudorapidity P separation between the two highest ET jets, and ET(gap), the total summed transverse energy between the jets. Rapidity gap events are defined as events in which ET(gap) is less than E T(cut), for ET(cut) varied between jets 0.5 and 2.0 GeV. The fraction of dijet events with a rapidity gap is measured differentially in Deltaeta, x(p)(jets) and x(gamma)(jets). An excess of events with rapidity gaps at low values of ET(cut) is observed above the expectation from standard photoproduction processes. This excess can be explained by the exchange of a strongly interacting colour singlet object between the jets.European Physical Journal C 09/2002; 24:517527. · 5.25 Impact Factor  [Show abstract] [Hide abstract]
ABSTRACT: A search for contributions from odderon  photon fusion to exclusive single pi0 production via ep > epi0N* in the photoproduction regime at HERA, at an average photon  proton centreofmass energy = 210 GeV, and for photon virtualities of Q2 < 0.01 GeV2 is reported. The measurement proceeded via detection of the pi0 decay photons, the leading neutron from the N* decay, and the scattered electron. No indication for an odderon contribution was found. An upper limit is presented for the cross section integrated in the "visible" range 0.02 GeV2 < t < 0.3 GeV2. It was derived as sigma(gammap > pi0N*) < 39 nb at 95 % CL. This excludes an odderon  photon fusion cross section of 400 nb as predicted by theory.Physics Letters B 09/2002; 544:3543. · 6.02 Impact Factor  [Show abstract] [Hide abstract]
ABSTRACT: A measurement of inclusive jet crosssections in deepinelastic ep scattering at HERA is presented based on data with an integrated luminosity of 21.1 pb(1). The measurement is performed for photon virtualities Q(2) between 5 and 100 GeV2, differentially in Q(2), in the jet transverse energy ET, in E T(2)/Q(2) and in the pseudorapidity eta(lab). With the renormalization scale mu(R) = ET, perturbative QCD calculations in nexttoleading order (NLO) give a good description of the data in most of the phase space. Significant discrepancies are observed only for jets in the proton beam direction with ET below 20 GeV and Q2 below 20 GeV2. This corresponds to the region in which NLO corrections are largest and further improvement of the calculations is thus of particular interest. (C) 2002 Elsevier Science B.V. All rights reserved.Physics Letters B 07/2002; · 6.02 Impact Factor  [Show abstract] [Hide abstract]
ABSTRACT: A search for contributions to the reaction ep→eπ0N∗ from photon–odderon fusion in the photoproduction regime at HERA is reported, at an average photon–proton centreofmass energy 〈W〉=215 GeV. The measurement proceeds via detection of the π0 decay photons, a leading neutron from the N∗ decay, and the scattered electron. No π0 signal is observed and an upper limit on the cross section for the photon–odderon fusion process of σ(γp→π0N∗)<49 nb at the 95% confidence level is derived, integrated over the experimentally accessible range of the squared fourmomentum transfer at the nucleon vertex 0.02<t<0.3 GeV2. This excludes a recent prediction from a calculation based on a nonperturbative QCD model of a photon–odderon fusion cross section above 200 nb.Physics Letters B 06/2002; 544:3543. · 6.02 Impact Factor  [Show abstract] [Hide abstract]
ABSTRACT: Dijet cross sections as functions of several jet observables are measured in photoproduction using the HI detector at HERA. The data sample comprises e(+)p data with an integrated luminosity of 319 pb(1). Jets are selected using the inclusive k(perpendicular to) algorithm with a minimum transverse energy of 25 GeV for the leading jet. The phase space covers longitudinal proton momentum fraction x(p) and photon longitudinal momentum fraction x(gamma) in the ranges 0.05 < x(p) < 0.6 and 0.1 < x(gamma) < 1. The predict ions of nextto leading order perturbative QCD, including recent photon and proton parton densities, are found to be compatible with the data in a wide kinematical range.European Physical Journal C 01/2002; 25:1323. · 5.25 Impact Factor  [Show abstract] [Hide abstract]
ABSTRACT: The helicity structure of the diffractive electroproduction of rho mesons, e + p > e + rho + Y, is studied in a previously unexplored region of large fourmomentum transfer squared at the proton vertex, t: 0 < t' < 3 GeV2, where t' = \t\  \t\ min. The data used are collected with the HI detector at HERA in the kinematic domain 2.5 < Q(2) < 60 GeV2, 40 < W < 120 GeV No t dependence of the r(00)(04) spin density matrix element is found. A significant t dependent helicity nonconservation from the virtual photon to the rho meson is observed for the spin density matrix element combinations r(00)(5) + 2r(11)(5) and r(00)(1) + 2r(11)(1). These t dependences are consistently described by a perturbative QCD model based on the exchange of two gluons. (C) 2002 Elsevier Science B.V. All rights reserved.Physics Letters B 01/2002; 539:2539. · 6.02 Impact Factor  [Show abstract] [Hide abstract]
ABSTRACT: Deepinelastic scattering data in the range 150 < Q(2) < 35000 GeV2 are used to investigate the minimum jet separation necessary to allow accurate description of the rate of dijet production using nexttoleading order perturbative QCD calculations. The required jet separation is found to be small, allowing about 1/3 of DIS data to be classified as dijet, as opposed to approximately 1/10 with more typical jet analyses. A number of precision measurements made using this dijet sample are well described by the calculations. The data are also described by the combination of leading order matrix elements and parton showers, as implemented in the QCD based Monte Carlo model RAPGAP.European Physical Journal C 01/2002; 24:3341. · 5.25 Impact Factor  [Show abstract] [Hide abstract]
ABSTRACT: The inclusive production of D∗±(2010) mesons in deepinelastic scattering is studied with the H1 detector at HERA. In the kinematic region 1Phys.Lett. 01/2002; B528:199214. 
Article: Search for excited neutrinos at HERA
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ABSTRACT: We present a search for excited neutrinos using e−p data taken by the H1 experiment at HERA at a centerofmass energy of 318 GeV with an integrated luminosity of 15 pb−1. No evidence for excited neutrino production is found. Mass dependent exclusion limits are determined for the ratio of the coupling to the compositeness scale, f/Λ, independently of the relative couplings to the SU(2) and U(1) gauge bosons. These limits extend the excluded region to higher masses than has been possible in previous searches at other colliders.Physics Letters B 01/2002; 525:916. · 6.02 Impact Factor  [Show abstract] [Hide abstract]
ABSTRACT: The total cross section for the photoproduction process with a leading proton in the final state has been measured at yp centreofmass energies W of 91, 181 and 231 GeV. The measured cross sections apply to the kinematic range with the transverse momentum of the scattered proton restricted to PT less than or equal to 0.2 GeV and 0.68 less than or equal to z less than or equal to 0.88, where z = E'(p)/Ep is the scattered proton energy normalised to the beam energy. The cross section d sigma (gammap>Xp')(W, z)/dz is observed to be independent of W and z within the measurement errors and amounts to (8.05 +/ 0.06 (stat) +/ 0.89 (syst)) Pb on average. The data are well described by a Triple Regge model in which the process is mediated by a mixture of exchanges with an effective Regge trajectory of intercept alpha (i)(0) = 0.33 +/ 0.04 (stat) +/ 0.04 (syst). The total cross section for the interaction of the photon with this mixture (gamma alpha (i) > X) can be described by an effective trajectory of intercept alpha (k) (0) = 0.99 +/ 0.01 (stat) +/ 0.05 (syst). Predictions based on previous triple Regge analyses of pp > pX data assuming vertex factorisation are broadly consistent with the yp data. The measured cross sections are compared with deep inelastic scattering leading proton data in the same region of z and p(T) for photon virtuality Q(2) > 2.5 GeV2. The ratio of the cross section for leading proton production to the total cross section is found to rise with Q(2). (C) 2001 Elsevier Science B.V. All rights reserved.Nuclear Physics B 12/2001; 619:321. · 3.95 Impact Factor  [Show abstract] [Hide abstract]
ABSTRACT: A measurement is presented of the cross section for D∗± meson production in diffractive deepinelastic scattering for the first time at HERA. The cross section is given for the process ep→eXY, where the system X contains at least one D∗± meson and is separated by a large rapidity gap from a low mass proton remnant system Y. The cross section is presented in the diffractive deepinelastic region defined by 2<Q2<100 GeV2, 0.05<y<0.7, , MY<1.6 GeV and t<1 GeV2. The D∗± mesons are restricted to the range GeV and . The cross section is found to be 246±54±56 pb and forms about 6% of the corresponding inclusive D∗± cross section. The cross section is presented as a function of various kinematic variables, including which is an estimate of the fraction of the momentum of the diffractive exchange carried by the parton entering the hardsubprocess. The data show a large component of the cross section at low where the contribution of the boson–gluonfusion process is expected to dominate. The data are compared with several QCDbased calculations.Physics Letters B 09/2001; 520:191203. · 6.02 Impact Factor  [Show abstract] [Hide abstract]
ABSTRACT: A measurement of the derivative (∂ lnF2/∂ lnx)Q2≡−λ(x,Q2) of the proton structure function F2 is presented in the low x domain of deeply inelastic positron–proton scattering. For 5×10−5⩽x⩽0.01 and , λ(x,Q2) is found to be independent of x and to increase linearly with lnQ2.Physics Letters B 08/2001; 520:183190. · 6.02 Impact Factor  [Show abstract] [Hide abstract]
ABSTRACT: A measurement is presented of elastic deeply virtual Compton scattering e++p→e++γ+p at HERA using data taken with the H1 detector. The cross section is measured as a function of the photon virtuality, Q2, and the invariant mass, W, of the γp system, in the kinematic range , and , where t is the squared momentum transfer to the proton. The measurement is compared to QCD based calculations.Physics Letters B 07/2001; 517:4758. · 6.02 Impact Factor  [Show abstract] [Hide abstract]
ABSTRACT: A search for scalar and vector leptoquarks coupling to first generation fermions is performed in the H1 experiment at the ep collider HERA. The analysis uses ep data collected in 1998 and 1999 at a centreofmass energy of 320 GeV, corresponding to an integrated luminosity of similar to 15 pb(1). No evidence for the direct production of such particles is found in a data sample with a large transverse momentum final state electron or with large missing transverse momentum, and constraints on leptoquark models are established. For a Yukawa coupling of electromagnetic strength leptoquarks are excluded for masses up to similar to 290 GeV. This analysis complements the leptoquark searches performed previously using data collected whilst HERA was operating with positrons instead of electrons. (C) 2001 Elsevier Science B.V. All rights reserved.Physics Letters B 07/2001; 523:234242. · 6.02 Impact Factor  [Show abstract] [Hide abstract]
ABSTRACT: The total cross section for the photoproduction process with a leading proton in the final state has been measured at γp centreofmass energies W of 91, 181 and 231 GeV. The measured cross sections apply to the kinematic range with the transverse momentum of the scattered proton restricted to pT⩽0.2 GeV and 0.68⩽z⩽0.88, where z=Ep′/Ep is the scattered proton energy normalised to the beam energy. The cross section dσγp→Xp′(W,z)/dz is observed to be independent of W and z within the measurement errors and amounts to μb on average. The data are well described by a Triple Regge model in which the process is mediated by a mixture of exchanges with an effective Regge trajectory of intercept . The total cross section for the interaction of the photon with this mixture (γαi→X) can be described by an effective trajectory of intercept . Predictions based on previous triple Regge analyses of pp→pX data assuming vertex factorisation are broadly consistent with the γp data. The measured cross sections are compared with deep inelastic scattering leading proton data in the same region of z and pT for photon virtuality . The ratio of the cross section for leading proton production to the total cross section is found to rise with Q2.Nuclear Physics B. 06/2001;
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Institutions

1993–1998

Deutsches ElektronenSynchrotron
Hamburg, Hamburg, Germany


1996

HumboldtUniversität zu Berlin
 Department of Physics
Berlin, Land Berlin, Germany


1994–1995

Yerevan Physics Institute
Ayrivan, Yerevan, Armenia


1988

Imperial College London
Londinium, England, United Kingdom


1986

Queen Mary, University of London
Londinium, England, United Kingdom


1982–1984

CERN
Genève, Geneva, Switzerland


1978–1984

The University of Sheffield
Sheffield, England, United Kingdom
