349 research outputs found
The Liquid Argon Jet Trigger of the H1 Experiment at HERA
We report on a novel trigger for the liquid argon calorimeter which was installed in the H1 Experiment at HERA.This trigger, called the “Jet Trigger”, was running at level 1 and implemented a real-time cluster algorithm. Within only 800 ns, the Jet Trigger algorithm found local energy maxima in the calorimeter, summed their immediate neighbors, sorted the resulting jets by energy, and applied topological conditions for the final level 1 trigger decision. The Jet Trigger was in operation from the year 2006 until the end of the HERA running in the summer of 2007. With the Jet Trigger it was possible to substantially reduce the thresholds for triggering on electronsand jets, giving access to a largely extended phase space for physical observables which could not have been reached in H1 before. The concepts of the Jet Trigger may be an interesting upgrade option for the LHC experiments
Search for Doubly-Charged Higgs Boson Production at HERA
A search for the single production of doubly-charged Higgs bosons H^{\pm \pm}
in ep collisions is presented. The signal is searched for via the Higgs decays
into a high mass pair of same charge leptons, one of them being an electron.
The analysis uses up to 118 pb^{-1} of ep data collected by the H1 experiment
at HERA. No evidence for doubly-charged Higgs production is observed and mass
dependent upper limits are derived on the Yukawa couplings h_{el} of the Higgs
boson to an electron-lepton pair. Assuming that the doubly-charged Higgs only
decays into an electron and a muon via a coupling of electromagnetic strength
h_{e \mu} = \sqrt{4 \pi \alpha_{em}} = 0.3, a lower limit of 141 GeV on the
H^{\pm\pm} mass is obtained at the 95% confidence level. For a doubly-charged
Higgs decaying only into an electron and a tau and a coupling h_{e\tau} = 0.3,
masses below 112 GeV are ruled out.Comment: 15 pages, 3 figures, 1 tabl
Forward pi^0 Production and Associated Transverse Energy Flow in Deep-Inelastic Scattering at HERA
Deep-inelastic positron-proton interactions at low values of Bjorken-x down
to x \approx 4.10^-5 which give rise to high transverse momentum pi^0 mesons
are studied with the H1 experiment at HERA. The inclusive cross section for
pi^0 mesons produced at small angles with respect to the proton remnant (the
forward region) is presented as a function of the transverse momentum and
energy of the pi^0 and of the four-momentum transfer Q^2 and Bjorken-x.
Measurements are also presented of the transverse energy flow in events
containing a forward pi^0 meson. Hadronic final state calculations based on QCD
models implementing different parton evolution schemes are confronted with the
data.Comment: 27 pages, 8 figures and 3 table
Searches at HERA for Squarks in R-Parity Violating Supersymmetry
A search for squarks in R-parity violating supersymmetry is performed in e^+p
collisions at HERA at a centre of mass energy of 300 GeV, using H1 data
corresponding to an integrated luminosity of 37 pb^(-1). The direct production
of single squarks of any generation in positron-quark fusion via a Yukawa
coupling lambda' is considered, taking into account R-parity violating and
conserving decays of the squarks. No significant deviation from the Standard
Model expectation is found. The results are interpreted in terms of constraints
within the Minimal Supersymmetric Standard Model (MSSM), the constrained MSSM
and the minimal Supergravity model, and their sensitivity to the model
parameters is studied in detail. For a Yukawa coupling of electromagnetic
strength, squark masses below 260 GeV are excluded at 95% confidence level in a
large part of the parameter space. For a 100 times smaller coupling strength
masses up to 182 GeV are excluded.Comment: 32 pages, 14 figures, 3 table
Top Quark Physics
We review the prospects for studies of the top quark at the LHC.We review the prospects for studies of the top quark at the LHC. Members of the working group who have contributed to this document are: A.Ahmadov, G.Azuelos, U.Baur, A.Belyaev, E.L.Berger, W.Bernreuther, E.E.Boos, M.Bosman, A.Brandenburg, R.Brock, M.Buice, N.Cartiglia, F.Cerutti, A.Cheplakov, L.Chikovani, M.Cobal-Grassmann, G.Corcella, F.del Aguila, T.Djobava, J.Dodd, V.Drollinger, A.Dubak, S.Frixione, D.Froidevaux, B.Gonzalez Pineiro, Y.P.Gouz, D.Green, P.Grenier, S.Heinemeyer, W.Hollik, V.Ilyin, C.Kao, A.Kharchilava, R. Kinnunen, V.V.Kukhtin, S.Kunori, L.La Rotonda, A.Lagatta, M.Lefebvre, K.Maeshima, G.Mahlon, S.Mc Grath, G.Medin, R.Mehdiyev, B.Mele, Z.Metreveli, D.O'Neil, L.H.Orr, D.Pallin, S.Parke, J.Parsons, D.Popovic, L.Reina, E.Richter-Was, T.G.Rizzo, D.Salihagic, M.Sapinski, M.H.Seymour, V.Simak, L.Simic, G.Skoro, S.R.Slabospitsky, J.Smolik, L.Sonnenschein, T.Stelzer, N.Stepanov, Z.Sullivan, T.Tait, I.Vichou, R.Vidal, D.Wackeroth, G.Weiglein, S.Willenbrock, W.W
Measurement of the charm and beauty structure functions using the H1 vertex detector at HERA
Inclusive charm and beauty cross sections are measured in e − p and e + p neutral current collisions at HERA in the kinematic region of photon virtuality 5≤Q 2≤2000 GeV2 and Bjorken scaling variable 0.0002≤x≤0.05. The data were collected with the H1 detector in the years 2006 and 2007 corresponding to an integrated luminosity of 189 pb−1. The numbers of charm and beauty events are determined using variables reconstructed by the H1 vertex detector including the impact parameter of tracks to the primary vertex and the position of the secondary vertex. The measurements are combined with previous data and compared to QCD predictions
Study of Charm Fragmentation into D^{*\pm} Mesons in Deep-Inelastic Scattering at HERA
The process of charm quark fragmentation is studied using meson
production in deep-inelastic scattering as measured by the H1 detector at HERA.
Two different regions of phase space are investigated defined by the presence
or absence of a jet containing the meson in the event. The
parameters of fragmentation functions are extracted for QCD models based on
leading order matrix elements and DGLAP or CCFM evolution of partons together
with string fragmentation and particle decays. Additionally, they are
determined for a next-to-leading order QCD calculation in the fixed flavour
number scheme using the independent fragmentation of charm quarks to
mesons.Comment: 33 pages, submitted to EPJ
Inelastic photoproduction of J/Psi mesons at HERA
An analysis of inelastic photoproduction of J/Psi mesons is presented using data collected at the ep collider HERA corresponding to an integrated luminosity of above 80pb-1. Differential and double differential cross sections are measured in a wide kinematic region: 6
Inelastic Leptoproduction of J/Psi Mesons at HERA
The leptoproduction of J/psi mesons is studied in inelastic reactions for
four momentum transfers 2<Q^2<100GeV^2. The data were taken with the H1
detector at the electron proton collider HERA and correspond to an integrated
luminosity of 77 pb-1. Single differential and double differential cross
sections are measured with increased precision compared with previous analyses.
New leading order calculations within the non-relativistic QCD factorisation
approach including colour octet and colour singlet contributions are compared
with the data and are found to give a reasonable description of most
distributions. An exception is the shape of the distribution in the J/psi
fractional energy, z, which deviates significantly from that of the data.
Comparisons with photoproduction are made and the polarisation of the produced
J/psi meson is analysed.Comment: 27 pages, 7 figures and 7 table
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