Y. Sirois

Theoretical and phenomenological implications of R-parity violation in supersymmetric theories are discussed in the context of particle physics and cosmology. Fundamental aspects include the relation with continuous and discrete symmetries and the various allowed patterns of R-parity breaking. Recent developments on the generation of neutrino masses and mixings within different scenarios of R-parity violation are discussed. The possible contribution of R-parity-violating Yukawa couplings in processes involving virtual supersymmetric particles and the resulting constraints are reviewed. Finally, direct production of supersymmetric particles and their decays in the presence of R-parity-violating couplings is discussed together with a survey of existing constraints from collider experiments.

The backward region of the H1 detector has been upgraded in order to provide improved measurement of the scattered electron in deep inelastic scattering events. The centerpiece of the upgrade is a high-resolution lead/scintillating-fibre calorimeter. The main design goals of the calorimeter are: good coverage of the region close to the beam pipe, high angular resolution and energy resolution of better than 2% for 30 GeV electrons. The calorimeter should be capable of providing coarse hadronic energy measurement and precise time information to suppress out-of-time background events at the first trigger level. It must be compact due to space restrictions. These requirements were fulfilled by constructing two separate calorimeter sections. The inner electromagnetic section is made of 0.5 mm scintillating plastic fibres embedded in a lead matrix. Its lead-to-fibre ratio is 2.3:1 by volume. The outer hadronic section consists of 1.0 mm diameter fibres with a lead-to-fibre ratio of 3.4:1. The mechanical construction of the new calorimeter and its assembly in the H1 detector are described.

Cross sections for elastic photoproduction of J/ψ and ϒ mesons are presented. For J/ψ mesons the dependence on the photon-proton centre-of-mass energy Wγp is analysed in an extended range with respect to previous measurements of 26≤Wγp≤285GeV. The measured energy dependence is parameterized as σγp∝Wγpδ with δ=0.83±0.07. The differential cross section dσ/dt for J/ψ mesons is derived, its dependence on Wγp and on t is analysed and the effective trajectory (in terms of Regge theory) is determined to be α(t)=(1.27±0.05)+(0.08±0.17)·t/GeV2. Models based on perturbative QCD and on pomeron exchange are compared to the data.

We present results on calibration runs performed with pions at the CERN SPS for different modules of the H 1 liquid argon calorimeter which consists of an electromagnetic section with lead absorbers and a hadronic section with steel absorbers. The data cover an energy range from 3.7 to 205 GeV. Detailed comparisons of the data and simulation with GHEISHA 8 in the framework of GEANT 3.14 are presented. The measured pion induced shower profiles are well described by the simulation. The total signal of pions on an energy scale determined from electron measurements is reproduced to better than 3% in various module configurations. After application of weighting functions, determined from Monte Carlo data and needed to achieve compensation, the reconstructed measured energies agree with simulation to about 3%. The energies of hadronic showers are reconstructed with a resolution of about 50%√E ⨸ 2%. This result is achieved by inclusion of signals from an iron streamer tube tail catcher behind the liquid argon stacks.

The reconstruction of the energy and momentum of isolated electrons in CMS combining tracking and electromagnetic calorimetry information is described. The emphasis is put on primary electrons with transverse momentum below 50 GeV/c. The energy deposited in the electromagnetic calorimeter is measured in clusters of clusters (superclusters) which collect bremsstrahlung photons emitted along the electron trajectory in the tracker volume. The electron tracks are built from seeds in the pixel detector found via a cluster-driven pixel hit matching algorithm, followed by a reconstruction of trajectories in the silicon strip tracker with a Gaussian sum filter. Electrons are classified using observables sensitive to the pattern of bremsstrahlung emission and electromagnetic showering in the tracker material. Energy scale corrections depending on the electron class are applied to the supercluster and estimates of associated errors are obtained. The electron energy is deduced from a weighted combination of the corrected supercluster energy and tracker momentum measurements. The electron direction is that of the reconstructed electron track at interaction vertex. The pre-selection of isolated electron candidates for physics analysis is described. Class-dependent observables combining tracking and calorimetry information are discussed for electron identification.

Results on J/ψ production in ep interactions in the H1 experiment at HERA are presented. The J/ψ mesons are produced by almost real photons (Q2 ≈ 0) and detected via their leptonic decays. The data have been taken in 1994 and correspond to an integrated luminosity of 2.7 pb−1. The γp cross section for elastic J/ψ production is observed to increase strongly with the center of mass energy. The cross section for diffractive J/ψ production with proton dissociation is found to be of similar magnitude as the elastic cross section. Distributions of transverse momentum and decay angle are studied and found to be in accord with a diffractive production mechanism. For inelastic J/ψ production the total γp cross section, the distribution of transverse momenta, and the elasticity of the J/ψ are compared to NLO QCD calculations in a colour singlet model and agreement is found. Diffractive ψ′ production has been observed and a first estimate of the ratio to J/ψ production in the HERA energy regime is given.

We describe the calorimeter system serving the HELIOS experiment at CERN, its calibration, and its performances measured in test experiments. The calorimeter signal for hadrons was found to be proportional to the energy to within 2% over the energy range 8–200 GeV. Over the same energy range the energy resolution σE scales as 1E for both electromagnetic and hadronic showers. The values found were (0.215 ± 0.007)E and (0.337 ± 0.012)E, respectively, for the detection of single particles. The signal ratios e/mip and eπ are 0.70 ± 0.05 and 0.984 ± 0.006, where the latter ratio was found to be dependent on the signal integration time the quoted number being obtained for a 130 ns gate. The energy resolution for multiparticle detection was found to be about twice as large as for the detection of single particles in the actual calorimeter configuration. The energy flow logic, designed to provide trigger information on physics quantities such as transverse energy and missing energy, was shown to be very accurate and reliable.

The result of a search at the LHC for heavy stable charged particles produced in pp collisions at $ \sqrt {s} = 7\;{\text{TeV}} $ is described. The data sample was collected with the CMS detector and corresponds to an integrated luminosity of 3.1 pb−1. Momentum and ionization-energy-loss measurements in the inner tracker detector are used to identify tracks compatible with heavy slow-moving particles. Additionally, tracks passing muon identification requirements are also analyzed for the same signature. In each case, no candidate passes the selection, with an expected background of less than 0.1 events. A lower limit at the 95% confidence level on the mass of a stable gluino is set at 398GeV/c 2, using a conventional model of nuclear interactions that allows charged hadrons containing this particle to reach the muon detectors. A lower limit of 311 GeV/c 2 is also set for a stable gluino in a conservative scenario of complete charge suppression, where any hadron containing this particle becomes neutral before reaching the muon detectors.

Hadronic event shapes have been measured in proton-proton collisions at sqrt(s)=7 TeV, with a data sample collected with the CMS detector at the LHC. The sample corresponds to an integrated luminosity of 3.2 inverse picobarns. Event-shape distributions, corrected for detector response, are compared with five models of QCD multijet production.

A measurement of the top-antitop production cross section in proton-proton collisions at a centre-of-mass energy of 7 TeV has been performed at the LHC with the CMS detector. The analysis uses a data sample corresponding to an integrated luminosity of 36 inverse picobarns and is based on the reconstruction of the final state with one isolated, high transverse-momentum electron or muon and three or more hadronic jets. The kinematic properties of the events are used to separate the top-antitop signal from W+jets and QCD multijet background events. The measured cross section is 173 + 39 - 32 (stat. + syst.) pb, consistent with standard model expectations.

The charge asymmetry in the production of top quark and antiquark pairs is measured in proton-proton collisions at a center-of-mass energy of 8 TeV. The data, corresponding to an integrated luminosity of 19.6 inverse femtobarns, were collected by the CMS experiment at the LHC. Events with a single isolated electron or muon, and four or more jets, at least one of which is likely to have originated from hadronization of a bottom quark, are selected. A template technique is used to measure the asymmetry in the distribution of differences in the top quark and antiquark absolute rapidities. The measured asymmetry is A[c,y] = [0.33 +/- 0.26 (stat) +/- 0.33 (syst)]%, which is the most precise result to date. The results are compared to calculations based on the standard model and on several beyond-the-standard-model scenarios.

The properties of final modules of a high resolution lead/scintillating-fibre calorimeter to upgrade the backward region of the H1 detector were studied with electrons in the energy range from 2–60 GeV. The electromagnetic calorimeter consists of scintillating fibres with a diameter of 0.5 mm embedded in a lead matrix. This small fibre radius, in combination with a lead-to-fibre ratio of 2.27:1, ensures excellent energy resolution which has been measured to be δ/E=7.1%/ E/GeV ⊕ 1.0%. The spatial resolution as a function of energy for impact points at the center of a cell is given by 4.4 mm/ E/GeV + 1.0 mm. The time resolution was found to be better than 0.4 ns.

The performances of the H1 liquid argon calorimeter modules for the energy measurements and identification of electrons are studied with test data taken at CERN in the energy range 5 to 166 GeV. Various electron identification estimators exploiting global or detailed shower characteristics are studied and compared. The usage of impact position measurements is also discussed. A best combination of robust shower estimators leads typically to π-misidentification probabilities in the range 1.5 to 5.0 × 10−3 at 30 GeV for 95% electron detection efficiency. This further reduces to ∼ 10−4 for these pions to be misidentified as electrons below 25 GeV.

The HELIOS experiment has measured inclusivep ⊥ spectra of negative particles in the rapidity region 1.0<y<1.9. The general shape of thep ⊥ spectra in p +W, O+W and S+W is similar, but cannot be described by a single exponential. Compared to p+p collisions, an excess is observed for low and highp ⊥. This effect increases with the projectile mass. Except for very lowE ⊥, the average transverse momentum <p ⊥> is found to be approximately constant up to the highest accessible values ofE ⊥.

We determined the number of fissions that occur in the development of a hadron shower in a 238U calorimeter, using a method based on the analysis of induced radioactivity. Measurements were done at 300 GeV (π−, and at 591 MeV (protons). The number of fissions turns out to be much smaller (∼ 10 fissions per GeV) than usually assumed, and is very sensitive to the calorimeter configuration. For example, in massive 238U the number of neutron-induced fissions is 25% larger than in a fine-sampling uranium/scintillator device. The results for calorimeters with a high-Z readout are similar to the massive U case. A significant fraction (10–15%) of the fissions are caused by fast charged particles rather than by slow neutrons. We also determined the total neutron production in the proton beam. It turns out that less than 25% of the neutrons produced in the shower development cause fission. The insertion of low-Z readout layers decisively determines how fast and by which mechanisms the neutrons lose their kinetic energy. The neutron flux in lead is about 40% of that in uranium, but the neutrons are on an average faster. We measured that 4.1 ± 0.4 fisions per GeV are on an average induced in the shower development of an incoming 300 GeV π. An attempt is made to explain these data. The consequences for calorimetric measurements of the hadron energy are discussed.

The acrylic scintillator which was used for several years as the active medium in the Axial Field Spectrometer uranium calorimeter at the CERN Intersecting Storage Rings was found to be severely damaged. The observed light output has decreased on the average by a factor of 2, and the attenuation length by a factor of 3, causing a severe degradation of the energy resolution of the system for the detection of both electromagnetic and hadronic showers. It could be shown that the effects are due to the radiation induced by uranium decay. The fact that the integrated dose obtained from this process (50 Gy) is 2 orders of magnitude smaller than what was currently believed to be a safe level, strongly suggests that the dose rate is a dominating factor in these radiation damage problems. It could be shown that the radiation resistivity is improved by at least an order of magnitude if contact with oxygen is avoided.

We report on the production of low-mass electron pairs and muon pairs in p-Be collisions at 450 GeV/c at the CERN SPS. For both electron and muon pairs the low-mass spectrum can be explained satisfactorily by lepton pairs from hadronic decays, and there is no need to invoke any "unconventional" source. The normalisation of the major hadronic sources is set by the data. The upper limit, at 90% confidence level, on any new source of lepton pairs is ∼20% of the hadronic decay contribution for muons, and ∼40% for electrons.

A review of searches for physics beyond the Standard Model carried out at high energy leptonhadron and hadron-hadron facilities is presented, with emphasis on topics of interest for future data taking at the upgraded Tevatron pp and HERA ep colliders. The status and discovery prospects are discussed for leptoquarks, Technicolour and supersymmetry, forbidden lepton and quark flavour-changing processes, extra gauge bosons, excited states of composite fermions, generic contact interactions and extra compactified dimensions.

The transverse energy distributions have been measured for interactions of 32S nuclei with Al, Ag, W, Pt, Pb, and U targets, at an incident energy of 200 GeV per nucleon in the pseudorapidity region −0.1 < νlab < 5.5. These distributions are compared with those for 16OW interactions in the same pseudorapidity region and with earlier measurements performed with 16O and 32S projectiles in the region −0.1 < νlab < 2.9. These comparisons provide both a better understanding of the dynamics involved and improved estimates of stopping power and energy density.

This Letter reports on a new search for the muon-number---nonconserving decay $\ensuremath{\mu}\ensuremath{\rightarrow}e\ensuremath{\gamma}\ensuremath{\gamma}$, using two large NaI(Tl) crystals. The new upper limit obtained is $R(\ensuremath{\mu}\ensuremath{\rightarrow}e\ensuremath{\gamma}\ensuremath{\gamma})&lt;8.4\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}9}$ (90% C.L.).

Diffractive dissociation of nuclei (Be, Al, W) in collisions with 450 GeV/c protons,pA→pX, has been measured with the HELIOS spectrometer at the CERN Super Proton synchrotron. The dependence of the single-diffraction cross-section on the nuclear massA can be parametrized as σSD mb×A 0.35±0.02, showing the peripheral nature of the process. The differential cross-section dσSD=(3.8±0.3)mb ×A 0.35±0.02, is exponential with the slope parameter, increasing from 6.2±0.4 (GeV/c)−2 for beryllium to 7.9±0.5 (GeV/c)−2 for tungsten. The slope parameter also increases with increasing massM X of the diffractively produced state. The rapidity, multiplicity, and transverse-momentum distributions of the particles of the diffractively produced stateX show a longitudinal phase-space population and are remarkably insensitive to the nuclear mass. This, together with theA 1/3 dependence of σSD, suggests that the dominant process of nuclear diffractive excitation is the dissociation of single nucleons.

Inclusive photonp ⊥ spectra were measured with 200 GeV/u proton,16O and32S beams on W and Pt targets, using a conversion method. The measurement of charged pions in the same apparatus allows a comparison of the γ data with the expected γ's from hadronic decays π0, η, η', ω). In all data sets, no deviation from the expected shape is observed in the range of 0.1<p ⊥<1.5 GeV/c. The number of photons normalized to pions agrees within the statistical (4%–11%) and systematical (9%) errors with the number of photons expected from hadronic decays in the integrated ranges ranges ofp ⊥>0.1 GeV/c andp ⊥>0.6 GeV/c.

Multiplicity distributions of charged particles produced in the pseudorapidity range 0.9 < ηlab < 5.5 were measured in oxygen-nucleus collisions for Al, Ag, and W target nuclei at incident energies of 60 and 200 GeV per nucleon. The multiplicity differential cross sections and the pseudorapidity distributions as a function of transverse energy are presented for the various target nuclei. The correlation between charged multiplicity and transverse energy is studied as a function of transverse energy. Data are compared with predictions of the IRIS and FRITIOF generators.

A prospective study for the observability of heavy neutral Higgs bosons decaying into supersymmetric particles at the Large Hadron Collider with the CMS detector is presented. The analysis focuses on the decay of the Higgs bosons into a pair of next-to-lightest neutralinos χ02, followed by the cascade down to the lightest neutralino, χ02 → l+l−χ01. The final state is characterized by the presence of four isolated leptons and missing transverse energy. The parameter space of the minimal supergravity model is explored and favourable regions for the observation of the A0/H0 bosons are identified. The A0/H0 bosons could be discovered in the 2e2μ channel in the mass region 250 ≲ mA/H ≲ 400 GeV/c2 with an integrated luminosity of 30 fb−1.

We have measured the inclusive cross-section as a function of missing energy, due to the production of neutrinos or new weakly interacting neutral particles in 450 GeV/c proton-nucleus collisions, using calorimetric measurements of visible event energy. Upper limits are placed on the production of new particles as a function of their energy. These upper limits are typically an order

A prospective analysis is presented for the discovery of the Standard Model Higgs boson in the CMS experiment at the LHC collider. The analysis focuses on the pp → H + X → ZZ(*) + X → e+e−e+e− + X channel for Higgs boson masses in the range 120 ≲ mH ≲ 300 GeV/c2. It relies on a full simulation of the detector response and usage of new detailed electron reconstruction tools. Emphasis is put on realistic strategies for the evaluation of experimental systematics and control of physics background processes. For an integrated LHC luminosity of 30fb−1, a Standard Model Higgs boson would be observed in the e+e−e+e− channel with a significance above 3 standard deviations for masses mH in the range from about 130 to 160 GeV/c2 and above 180 GeV/c2. A discovery with a significance above 5 standard deviations is possible for this integrated luminosity around mH ≃ 150 GeV/c2 and in the range from about 190 to 300 GeV/c2. The mass (cross-section) of the Higgs boson can be determined with a precision better than 1% (30%).

A search is performed for the production of a massive W′ boson decaying to a top and a bottom quark. The data analysed correspond to an integrated luminosity of 19.7 fb−1 collected with the CMS detector at the LHC in proton-proton collisions at $$ \sqrt{s}=8 $$ TeV. The hadronic decay products of the top quark with high Lorentz boost from the W′ boson decay are detected as a single top flavoured jet. The use of jet substructure algorithms allows the top quark jet to be distinguished from standard model QCD background. Limits on the production cross section of a right-handed W′ boson are obtained, together with constraints on the left-handed and right-handed couplings of the W′ boson to quarks. The production of a right-handed W′ boson with a mass below 2.02 TeV decaying to a hadronic final state is excluded at 95% confidence level. This mass limit increases to 2.15 TeV when both hadronic and leptonic decays are considered, and is the most stringent lower mass limit to date in the tb decay mode.

Hadronic response and electron identification performance of the new H1 lead-scintillating fibre calorimeter are investigated in the 1 to 7 GeV energy range using data taken at the CERN Proton Synchrotron. The energy response to minimum ionizing particles and interacting pions are studied and compared to Monte Carlo simulations. The measured energy of pions interacting either in the electromagnetic or in the hadronic section is found to scale linearly with the incident energy, providing an energy resolution σE ∼ 38% within a depth of one interaction length and σE ∼ 29% for a total depth of two interaction lengths. Several electron identification estimators are studied and combined as a function of energy and impact point. The probability for pions to be misidentified as electrons of any measured energy above 1 GeV ranges from 5% (for 2 GeV incident pions) to 0.4% (at 7 GeV) for an electron detection efficiency of 90%. The probability for pions of a given energy to be misidentified as electrons of the same energy falls to 0.25% at 7 GeV.

Results from the HELIOS External Spectrometer on kaon production in 200 GeV/A S + W and p + W collisions are presented. The Kπ ratios are compared with results from a lower beam energy and are found to be remarkably similar. Evidence for secondary production of K+ by meson-baryon rescattering is reviewed. Our results at y = 1.0–1.5 are compared with neutral strange particle results at midrapidity.

The discovery of the Higgs boson at a mass around 125 GeV by the ATLAS and CMS experiments at the LHC collider in 2012 establishes a new landscape in high-energy physics. The analysis of the full data sample collected with pp collisions at centre-of-mass energies of 7 and 8 TeV has allowed for considerable progress since the discovery. A review of the latest results is presented. La découverte du boson de Higgs à une masse proche de 125 GeV par les expériences ATLAS et CMS auprès du collisionneur LHC en 2012 a redéfini le paysage de la physique des hautes énergies. L'analyse de l'ensemble complet des données collectées en collisions pp à des énergies dans le centre de masse de 7 et 8 TeV a permis des progrès considérables depuis la découverte. Une revue des derniers résultats est présentée.

We present measurements of the rapidity and transverse-momentum distributions of the protons emitted in S+W, O+W, andp+W reactions at 200 GeV/A around the target rapidity (y=1). The rapidity density rises linearly with the transverse energy for all three systems, but the slope forp+W is much steeper than for O+W and S+W. The rapidity density forp+W is much higher than predicted by summing single nucleonnucleon collisions without any nuclear effects, indicating substantial rescattering of the produced particles. The predictions of the VENUS 3 model, including rescattering, show reasonable agreement with the data for all three systems. We do not have evidence for a strong collective flow of the outgoing particles.

A review of searches for physics beyond the Standard Model carried out at high energy lepton-hadron and hadron-hadron facilities is presented, with emphasis on topics of interest for future data taking at the upgraded Tevatron $p{\bar p}$ and HERA $ep$ colliders. The status and discovery prospects are discussed for leptoquarks, Technicolour and supersymmetry, forbidden lepton and quark flavour-changing processes, extra gauge bosons, excited states of composite fermions, generic contact interactions and extra compactified dimensions.

We report on the production ofe ± μ∓ pairs in 450 GeV/c pBe collisions at the CERN SPS. Theeμ signal, which has average missing energy of 21 GeV, is shown to be consistent with expectations from charm decay, and implies a σ ×B for $$c\bar c$$ production in p-nucleon collisions of 0.63 ± 0.35μb. Alternatively, using an estimate of charm production from other experiments, the data imply a 95% confidence level upper limit of 1.16μb on any new physics process which producese ± μ ∓.

The ionization probes used for monitoring the liquid argon purity in the H1 calorimeter are described and results of their operation in tests at CERN and during the period 1992 to the end of 1998 at HERA are given.The high sensitivity of the charge measurements leads to refined charge collection models, and to the observation of a variation of the ionization yield of our electron sources with temperature.

A overview of the ATLAS and CMS detectors and first physics results from the 2010 data taking campaign at the LHC collider is presented. Measurements with pp collisions at s=7TeV and for integrated luminosities reaching up to about 40 pb−1 are summarized for weak bosons and top quark production, as well as for the search of the Higgs Boson(s), supersymmetry and new interactions at the TeV scale. The physics prospects for the complete Run I from 2010 to 2012 with a few fb−1 of luminosity collected per experiment are discussed.

The new lead/scintillating-fibre calorimeter (“SpaCal”) for the backward region of the H1 experiment at HERA (DESY) is equipped with fine mesh phototubes which operate in a magnetic field close to 1 T. A large sample of these tubes of the types Hamamatsu R5505 and R5506, and Hamamatsu R2490-05, have been tested in fields of up to 1.2T. We have investigated the cathode homogeneity with and without magnetic field, the gain loss under the influence of the magnetic field, and stability with time. For a subsample of tubes, we have performed additional studies on stability with respect to temperature changes, variation of gain as a function of the magnetic field, high voltage discharges, single photo-electron response, and linearity. We finally summarize the experience with these tubes after one year of operation in the experiment.

The results of two sets of transverse energy measurements, performed with incident proton beams of 200 and 450 GeV/c momentum on several nuclear targets, are presented. The transverse energy cross sections dσ/dE T are measured in a pseudorapidity range including the target fragmentation region (−0.1<η<2.9) for both data sets and also in a nearly complete pseudorapidity coverage (−0.1<η<5.5) for the data taken at 200 GeV/c incident momentum. A comparison is made of the transverse energy distributions in the target fragmentation region and in the full η region. We find that the mean value of pseudorapidity of the dE T /dη distributions shifts towards the target fragmentation region as the atomic mass number of the target increases or a selection of high transverse energy events is made. A parametrization based on a simple geometrical nucleonnucleon scattering approach was found to be inadequate to describe all features of the transverse energy distributions. Finally, the VENUS model is compared with the experimental data.

A prospective analysis for the discovery of a light standard model Higgs boson in the CMS experiment at the large hadron collider is presented. The analysis focuses on the inclusive single production p + p → H + X and the Higgs boson decay channel H → WW ( * ) → e + νe - ν, for a Higgs boson mass M H in the range 120 < M H < 160 GeV/c 2 . A full simulation of the detector response is performed and detailed electron, jet and missing transverse energy reconstruction algorithms are used. Emphasis is put on a realistic treatment of background contamination and systematics. A Higgs boson of mass M H ≥ 134 GeV/c 2 would be observed with a significance above three standard deviations in the e + νe - ν channel alone for an integrated LHC luminosity above 30 fb -1 .

The electronic system developed for the SpaCal lead/scintillating-fibre calorimeters of the H1 detector in operation at the HERA ep collider is described in detail and the performance achieved during H1 data-taking is presented. The 10 MHz bunch crossing rate of HERA puts severe constraints on the requirements of the electronics. The energy and time readout are performed respectively with a 14-bit dynamic range and with a resolution of about 0.4 ns. The trigger branch consists of a nanosecond-resolution calorimetric time-of-flight for background rejection and an electron trigger based on analog `sliding windows'. The on-line background rejection currently achieved is o(10**6). The electron trigger allows a low energy trigger threshold to be set at about 0.50 +/- 0.08 (RMS) GeV with an efficiency >99.9%. The energy and time performance of the readout and trigger electronics is based on a newly-developed low noise (sigma_noise ca. 0.4 MeV) wideband (f < 200 MHz) preamplifier located at the output of the photomultipliers which are used for the fibre light readout in the ca. 1 Tesla magnetic field of H1.

The reconstruction of the four-momentum of electrons in CMS combining tracking and electromagnetic calorimetry information is described.Electrons in the energy range from 5 to 100 GeV are considered. Different electron topologies, depending on the amount of bremsstrahlung and re-interaction in the inner tracker material, are identified to select the most adapted energy scale correction for the electron supercluster and to estimate the associated error. The electron tracks are built starting from a cluster-driven seed finding in the pixel detector, followed by a Gaussian Sum Filter technique to build and fit trajectories in the Silicon Tracker Detectors. The electron four-momentum is deduced from a combination of the supercluster energy and tracker momentum measurements, with the direction taken from the electron track at interaction vertex.

This report summarizes the work of the "R-parity violation group" of the French Research Network (GDR) in Supersymmetry, concerning the physics of supersymmetric models without conservation of R-parity at HERA, LEP, Tevatron and LHC and limits on R-parity violating couplings from various processes. The report includes a discussion of the recent searches at the HERA experiment, prospects for new experiments, a review of the existing limits, and also theoretically motivated alternatives to R-parity and a brief discussion on the implications of R-parity violation on the neutrino masses.

The discovery of the Higgs boson at a mass around 125 GeV by the ATLAS and CMS experiments at the LHC collider in 2012 establishes a new landscape in high energy physics. The analysis of the full data sample collected with pp collisions at 7 and 8 TeV during run I has allowed for considerable progress since the discovery. A review of the latest results is presented.

The discovery of the Higgs boson at a mass around 125 GeV by the ATLAS and CMS experiments at the LHC collider in 2012 establishes a new landscape in high energy physics. The analysis of the full data sample collected with pp collisions at 7 and 8 TeV during run I has allowed for considerable progress since the discovery. A review of the latest results is presented.

A search for massive resonances decaying to a Z boson and a photon is performed in events with a hadronically decaying Z boson candidate, separately in light-quark and b quark decay modes, identified using jet substructure and advanced b tagging techniques. Results are based on samples of proton-proton collisions collected with the CMS detector at the LHC at center-of-mass energies of 8 and 13 TeV, corresponding to integrated luminosities of 19.7 and 2.7 inverse femtobarns, respectively. The results of the search are combined with those of a similar search in the leptonic decay modes of the Z boson, based on the same data sets. Spin-0 resonances with various widths and with masses in a range between 0.2 and 3.0 TeV are considered. No significant excess is observed either in the individual analyses or the combination. The results are presented in terms of upper limits on the production cross section of such resonances and constitute the most stringent limits to date for a wide range of masses.

The inelastic hadronic cross section in proton-lead collisions at a centre-of-mass energy per nucleon pair of 5.02 TeV is measured with the CMS detector at the LHC. The data sample, corresponding to an integrated luminosity of 12.6 +/- 0.4 inverse nanobarns, has been collected with an unbiased trigger for inclusive particle production. The cross section is obtained from the measured number of proton-lead collisions with hadronic activity produced in the pseudorapidity ranges 3<abs(eta)<5 and/or -5<abs(eta)<-3, corrected for photon-induced contributions, experimental acceptance, and other instrumental effects. The inelastic cross section is measured to be sigma[inel,pPb]=2061 +/- 3 (stat) +/- 34 (syst) +/- 72 (lum) mb. Various Monte Carlo generators, commonly used in heavy ion and cosmic ray physics, are found to reproduce the data within uncertainties. The value of sigma[inel,pPb] is compatible with that expected from the proton-proton cross section at 5.02 TeV scaled up within a simple Glauber approach to account for multiple scatterings in the lead nucleus, indicating that further net nuclear corrections are small.

Three calorimeter modules made of scintillating fibres embedded in a lead matrix were tested at the CERN Proton Synchrotron. The linearity of the energy response to electron-induced showers, measured in a module having a lead-to-fibre volume ratio of 1.8, is verified within 2.5% whilst the energy resolution is found to be 9.6%E + 1% at 6° and 4° impact angles in the horizontal and vertical planes. An impact position resolution of 1.51 mmE + 1.45 mm is achieved. The e/π± separation based on the longitudinal and transverse shower size is discussed for various calorimeter configurations. Requiring an energy above a threshold of 3 GeV leads to a π± rejection factor of 12 to 36 with longitudinal criterium, and a π± rejection factor of 43 to 100 with a transverse cut in a π± energy range of 3 to 7 GeV. A combination of both criteria leads to a rejection factor between 116 and 303 in the same energy range. The study of the time shape of the signals shows a very small intrinsic jitter of 0.4 ns on the calorimeter signals. It does not show any evidence of a detectable neutronic tail in π± signals.

The discovery of a new boson with a mass around 125 GeV has been established in July 2012 by the ATLAS and CMS experiments at the LHC collider. More than twice as much data was collected by the end of 2012. The analysis of the full data sample, collected with pp collisions at 7 and 8 TeV in 2011 and 2012, has now allowed for considerable progress in understanding the nature of the new boson. The new boson is found to be a Higgs boson, with properties as expected for the scalar boson H resulting from the Brout–Englert–Higgs mechanism responsible for electroweak symmetry breaking in the standard model. A review of the latest ATLAS and CMS results on the H boson is presented here.

A measurement of the ttbar production cross section at sqrt(s)=13 TeV is presented using proton-proton collisions, corresponding to an integrated luminosity of 2.3 inverse femtobarns, collected with the CMS detector at the LHC. Final states with one isolated charged lepton (electron or muon) and at least one jet are selected and categorized according to the accompanying jet multiplicity. From a likelihood fit to the invariant mass distribution of the isolated lepton and a jet identified as coming from the hadronization of a bottom quark, the cross section is measured to be sigma(ttbar)= 835 +/- 3 (stat) +/- 23 (syst) +/- 23 (lum) pb, in agreement with the standard model prediction. Using the expected dependence of the cross section on the pole mass of the top quark (m[t]), the value of m[t] is found to be 172.7+2.4-2.7 GeV.

This note describes a study of intermediate and heavy (masses considered 250, 300, 400, 500, 600 and 800 GeV/c) mass Higgs boson production via Weak Boson Fusion (WBF) using the CMS detector at LHC. Having the second largest production cross section, WBF is one of the main process, where the Higgs particle can be found. Evaluated LHC integrated luminosity should be more than 500 fb−1, when the mass of Higgs particle is expected to be in a range 250 400 GeV/c and more than 1000 fb−1 when mass of Higgs particle is expected to be in a range 500 1000 GeV/c. 1) e-mail: alexi.mestvirishvili@cern.ch

A prospective analysis for the discovery of a light standard model Higgs boson in the CMS experiment at the large hadron collider is presented. The analysis focuses on the inclusive single production p + p → H + X and the Higgs boson decay channel , for a Higgs boson mass MH in the range 120 < MH < 160GeV/c2. A full simulation of the detector response is performed and detailed electron, jet and missing transverse energy reconstruction algorithms are used. Emphasis is put on a realistic treatment of background contamination and systematics. A Higgs boson of mass MH 134GeV/c2 would be observed with a significance above three standard deviations in the channel alone for an integrated LHC luminosity above 30 fb−1.

The performance of the CMS PbWO4 electromagnetic calorimeter is discussed. Inter-calibration and electron energy measurements are presented based on data collected from 2004 to 2006 with an electron beam and with cosmic muons, using fully equipped supermodules of the CMS detector barrel.

Searches at the e-p collider HERA for supersymmetric partners of the Standard Model fermions are presented. Assuming R-parity conservation, selectrons and squarks of the Minimal Supersymmetric Standard Model are excluded for masses up to 65 GeV in a new region of the standard parameter space. Admitting in addition a R-parity violating Yukawa coupling $λ'$, squarks are sought through direct e-q fusion in a yet unexplored mass-coupling domain, taking into account all possible squark decays. Squark masses up to 240 GeV are excluded for $λ' \gtrsim \sqrt{4 πα_{em}}$, depending only weakly on the free model parameters.

Efficiency and precision in electron reconstruction is of ultimate importance for Higgs boson search at LHC through Higgs decay to four electrons. Main problems in electron reconstruction at CMS are reviewed and solution proposed

Progress in the simulaction and analysis of the Higgs decay to the 4 electrons via ZZ* intermediate state

New results in Higgs to ZZ* to 4 electron channel are reported with emphasis on electron reconstruction tools and framework for overall analysis

Electron reconstruction in CMS is presented, with emphasis on estimation of momentum, classification, identification and selection.

Status report of the work on detailed simulation of the Higgs decay to 4 electrons is given.

Searches for R-parity violating supersymmetry performed at the H1 experiment are presented. Emphasis is put on searches for squarks, which may be resonantly produced at the HERA $ep$ collider in supersymmetry where R-parity is violated. The preliminary results presented here were obtained using data collected at a centre-of-mass energy of 320 GeV and corresponding to an integrated luminosity of 63 pb$^{-1}$.

A review of the experimental searches for physics beyond the Standard Model performed at collider facilities is presented. The emphasis is put on topics of interest for future data-taking at the upgraded Tevatron pp and HERA ep colliders. The status and discovery prospects for leptoquarks, lepton flavour violation, technicolour, R-parity violating supersymmetry, flavour-changing neutral currents, excited fermions and contact interactions is discussed.

The phenomenology and prospects for a discovery of R-parity violating Supersymmetry at HERA are analysed. Emphasis is put on the direct resonant production of squarks by electron-quark fusion and all possible subsequent decay modes of the squarks are considered. In particular, the full consequences of the mixing in the supersymmetric gaugino-higgsino sector are taken into account. A rich phenomenology emerges for HERA which offers a unique sensitivity to new R-parity violating couplings and good discriminating power against free parameters of the theory.

Deep inelastic physics and the discovery reach beyond the Standard Model at existing and future ep colliders is discussed with an emphasis on the search for new bosons coupling to lepton-quark pairs.

The early observation at HERA of an excess of events compared to the expectation from the Standard Model in very short distance $e^+p$ deep-inelastic scattering processes has renewed the interest in the search for new physics which could manifest in electroweak-like interactions. New preliminary results from the H1 and ZEUS experiments making use of all available $e^+p$ data are reviewed here, with an emphasis on the search for new bosons possessing Yukawa couplings to lepton-quark pairs. The sensitivity of HERA to leptoquarks, and to squarks of R-parity violating supersymmetry, is confronted to existing indirect constraints from rare and forbidden semi-leptonic decays, atomic parity violation and neutrinoless double-beta decay, as well as to direct constraints from LEP and Tevatron colliders. The HERA and Tevatron colliders are found to offer exciting prospects for new physics, accessing yet unexplored domains of the mass-coupling plane. Possible striking manifestation of explicit lepton flavour violation is also discussed.

The early observation at HERA of an excess of events compared to the expectation from the Standard Model in very short distance $e^+p$ deep-inelastic scattering processes has renewed the interest in the search for new physics which could manifest in electroweak-like interactions. New preliminary results from the H1 and ZEUS experiments making use of all available $e^+p$ data are reviewed here, with an emphasis on the search for new bosons possessing Yukawa couplings to lepton-quark pairs. The sensitivity of HERA to leptoquarks, and to squarks of R-parity violating supersymmetry, is confronted to existing indirect constraints from rare and forbidden semi-leptonic decays, atomic parity violation and neutrinoless double-beta decay, as well as to direct constraints from LEP and Tevatron colliders. The HERA and Tevatron colliders are found to offer exciting prospects for new physics, accessing yet unexplored domains of the mass-coupling plane. Possible striking manifestation of explicit lepton flavour violation is also discussed.

The early observation at HERA of an excess of events compared to the expectation from the Standard Model in very short distance $e^+p$ deep-inelastic scattering processes has renewed the interest in the search for new physics which could manifest in electroweak-like interactions. New preliminary results from the H1 and ZEUS experiments making use of all available $e^+p$ data are reviewed here, with an emphasis on the search for new bosons possessing Yukawa couplings to lepton-quark pairs. The sensitivity of HERA to leptoquarks, and to squarks of R-parity violating supersymmetry, is confronted to existing indirect constraints from rare and forbidden semi-leptonic decays, atomic parity violation and neutrinoless double-beta decay, as well as to direct constraints from LEP and Tevatron colliders. The HERA and Tevatron colliders are found to offer exciting prospects for new physics, accessing yet unexplored domains of the mass-coupling plane. Possible striking manifestation of explicit lepton flavour violation is also discussed.