712 research outputs found
Hector, a fast simulator for the transport of particles in beamlines
Computing the trajectories of particles in generic beamlines is an important
ingredient of experimental particle physics, in particular regarding near-beam
detectors. A new tool, Hector, has been built for such calculations, using the
transfer matrix approach and energy corrections. The limiting aperture effects
are also taken into account. As an illustration, the tool was used to simulate
the LHC beamlines, in particular around the high luminosity interaction points
(IPs), and validated with results of the Mad-X simulator. The LHC beam
profiles, trajectories and beta functions are presented. Assuming certain
forward proton detector scenarios around the IP5, acceptance plots, irradiation
doses and chromaticity grids are produced. Furthermore, the reconstruction of
proton kinematic variables at the IP (energy and angle) is studied as well as
the impact of the misalignment of beamline elements.Comment: 40 pages, 20 figures; added references, corrected typos ; submitted
to JINS
DELPHES 3, A modular framework for fast simulation of a generic collider experiment
The version 3.0 of the DELPHES fast-simulation is presented. The goal of
DELPHES is to allow the simulation of a multipurpose detector for
phenomenological studies. The simulation includes a track propagation system
embedded in a magnetic field, electromagnetic and hadron calorimeters, and a
muon identification system. Physics objects that can be used for data analysis
are then reconstructed from the simulated detector response. These include
tracks and calorimeter deposits and high level objects such as isolated
electrons, jets, taus, and missing energy. The new modular approach allows for
greater flexibility in the design of the simulation and reconstruction
sequence. New features such as the particle-flow reconstruction approach,
crucial in the first years of the LHC, and pile-up simulation and mitigation,
which is needed for the simulation of the LHC detectors in the near future,
have also been implemented. The DELPHES framework is not meant to be used for
advanced detector studies, for which more accurate tools are needed. Although
some aspects of DELPHES are hadron collider specific, it is flexible enough to
be adapted to the needs of electron-positron collider experiments.Comment: JHEP 1402 (2014
High energy photon interactions at the LHC
Experimental prospects for studying high-energy photon-photon and
photon-proton interactions at the CERN Large Hadron Collider (LHC) are
discussed. Cross sections are calculated for many electroweak and beyond the
Standard Model processes. Selection strategies based on photon interaction
tagging techniques are studied. Assuming a typical LHC multipurpose detector,
various signals and their irreducible backgrounds are presented after applying
acceptance cuts. Prospects are discussed for the Higgs boson search, detection
of supersymmetric particles and of anomalous quartic gauge couplings, as well
as for the top quark physics.Comment: 17 pages, 16 tables and 14 figure
Single top quark photoproduction at the LHC
High-energy photon-proton interactions at the LHC offer interesting
possibilities for the study of the electroweak sector up to TeV scale and
searches for processes beyond the Standard Model. An analysis of the W
associated single top photoproduction has been performed using the adapted
MadGraph/MadEvent and CalcHEP programs interfaced to the Pythia generator and a
fast detector simulation program. Event selection and suppression of main
backgrounds have been studied. A comparable sensitivity to |V_{tb}| to those
obtained using the standard single top production in pp collisions has been
achieved already for 10 fb^{-1} of integrated luminosity. Photoproduction at
the LHC provides also an attractive framework for observation of the anomalous
production of single top due to Flavour-Changing Neutral Currents. The
sensitivity to anomalous coupling parameters, k_{tu\gamma} and k_{tc\gamma} is
presented and indicates that stronger limits can be placed on anomalous
couplings after 1 fb^{-1}
Sensitivity to anomalous quartic gauge couplings in photon-photon interactions at the LHC
The exclusive two-photon production at the LHC of pairs of W and Z bosons
provides a novel and unique test-ground for the electroweak gauge boson sector.
In particular it offers, thanks to high gamma-gamma center-of-mass energies,
large and direct sensitivity to the anomalous quartic gauge couplings otherwise
very difficult to investigate at the LHC. An initial analysis has been
performed assuming leptonic decays and generic acceptance cuts. Simulation of a
simple counting experiment has shown for the integrated luminosity of 10 fb-1
at least four thousand times larger sensitivity to the genuine quartic
couplings, a_0^W, a_0^Z, a_C^W and a_C^Z, than those obtained at LEP. The
impact of the unitarity constraints on the estimated limits has been studied
using the dipole form-factors. Finally, differential distributions of the decay
leptons have been provided to illustrate the potential for further improvements
of the sensitivities.Comment: 8 pages and 11 figures, Contribution to the CERN workshop on "High
energy photon collisions at the LHC", 22-25 April 200
As an Introduction: Quest for New Physics in Photon-Photon Interactions at the LHC
A significant fraction of pp collisions at the LHC will involve (quasi-real)
photon interactions occurring at energies well beyond the electroweak energy
scale. Hence, the LHC can to some extend be considered as a high-energy
photon-photon or photon-proton collider. This offers a unique possibility for
novel and complementary research where the available effective luminosity is
small, relative to parton-parton interactions, but it is compensated by better
known initial conditions and usually simpler final states. This is in a way a
method for approaching some of the issues to be addressed by the future lepton
collider. Such studies of photon interactions are possible at the LHC, thanks
to the striking experimental signatures of events involving photon exchanges,
in particular the presence of very forward scattered protons.Comment: 5 pages, 2 figures; Contribution to Proceedings of the CERN workshop
on High Energy Photon Collisions at the LHC, April 21-25, 200
Top Partner Discovery in the channel at the LHC
In this paper we study the discovery potential of the LHC run II for heavy
vector-like top quarks in the decay channel to a top and a boson. Despite
the usually smaller branching ratio compared to charged-current decays, this
channel is rather clean and allows for a complete mass reconstruction of the
heavy top. The latter is achieved in the leptonic decay channel of the
boson and in the fully hadronic top channel using boosted jet and jet
substructure techniques. To be as model-independent as possible, a simplified
model approach with only two free parameters has been applied. The results are
presented in terms of parameter space regions for evidence or
discovery for such new states in that channel.Comment: 24 pages, 8 figures, version 2 updated to JHEP 01 (2015) 08
Search for a narrow charmed baryonic state decaying to D^*+/- p^-/+ in ep collisions at HERA
A resonance search has been made in the D^*+/- p^-/+ invariant-mass spectrum
with the ZEUS detector at HERA using an integrated luminosity of 126 pb^-1. The
decay channels D^*+ -> D^0 pi^+_s -> (K^- pi^+) pi^+_s and D^*+ -> D^0 pi^+_s
-> (K^- pi^+ pi^+ pi^-) pi^+_s (and the corresponding antiparticle decays) were
used to identify D^*+/- mesons. No resonance structure was observed in the
D^*+/- p^-/+ mass spectrum from more than 60000 reconstructed D^*+/- mesons.
The results are not compatible with a report of the H1 Collaboration of a
charmed pentaquark, Theta^0_c.Comment: 22 pages, 7 figures, 1 table; minor text revisions; 2 references
adde
An NLO QCD analysis of inclusive cross-section and jet-production data from the ZEUS experiment
The ZEUS inclusive differential cross-section data from HERA, for charged and
neutral current processes taken with e+ and e- beams, together with
differential cross-section data on inclusive jet production in e+ p scattering
and dijet production in \gamma p scattering, have been used in a new NLO QCD
analysis to extract the parton distribution functions of the proton. The input
of jet data constrains the gluon and allows an accurate extraction of
\alpha_s(M_Z) at NLO;
\alpha_s(M_Z) = 0.1183 \pm 0.0028(exp.) \pm 0.0008(model)
An additional uncertainty from the choice of scales is estimated as \pm
0.005. This is the first extraction of \alpha_s(M_Z) from HERA data alone.Comment: 37 pages, 14 figures, to be submitted to EPJC. PDFs available at
http://durpdg.dur.ac.uk/hepdata in LHAPDFv
- …