P. Jarry

Search for Heavy Stable Charged Particles in pp collisions at sqrt(s)=7 TeV

The result of a search at the LHC for heavy stable charged particles produced in pp collisions at

First measurement of hadronic event shapes in pp collisions at √s=7 TeV

\sqrt {s} = 7\;{\text{TeV}}

Search for new heavy quarks in

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/c2, 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/c2 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.

e^+e^-

Hadronic event shapes have been measured in proton-proton collisions at √ 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 pb−1. Event-shape distributions, corrected for detector response, are compared with five models of QCD multijet production. Submitted to Physics Letters B ∗See Appendix A for the list of collaboration members ar X iv :1 10 2. 00 68 v1 [ he pex ] 1 F eb 2 01 1

collisions up to 46.78 GeV cm energy

Abstract The total e + e − annihilation onto hadron has been measured at CM energies between 33.00 and 36.72 GeV and between 38.66 and 46.78 GeV in steps of 20 and 30 MeV respectively. The average of the ratio R = σ ( e + e − → hadrons )/ σ is 〈 R 〉=3.85±0.12 and 〈 R 〉=4.04±0.10 for the two energy ranges. The systematic error on 〈 R 〉 is 0.31. Both values are consistent with the expectation for the known coloured quarks u, d, s, c and b. No evidence was found for the production of new quarks. If the largest fluctuation in R is interpreted as a narrow resonance, it corresponds to a product of the electronic width and the hadronic branching ratio Γ ee B had >2.9 keV at the 95% confidence level, well below the value expected for the toponium vector ground state with charge 2 3 e . The observed number of aplanar final states rules out the continuum production of a a new heavy flavour with pointlike cross section up to a CM energy of 45.4 GeV for a quarck charge of 1 3 e . and up to 46.6 GeV for 2 3 e at the 95% confidence level.

On the model dependence of the determination of the strong coupling constant in second order QCD from e+e−-annihilation into hadrons

Abstract Hadronic events obtained with the CELLO detector at PETRA are compared with second order QCD predictions using different models for the fragmentation of quarks and gluons into hadrons. We find that the model dependence in the determination of the strong coupling constant persists when going from first to second order QCD calculations.

Observation of a multiparticle event with two isolated energetic muons in e+e- interactions

Abstract An event from e+e− annihilation at √s = 43.450 GeV containing two topologically isolated energetic muons and two hadronic jets has been observed. The masses of the μ−μ, jet-jet and μ-jet combinations are all large. The expected number of such events from known processes is about 10−3.

EXCITED LEPTON SEARCH

Abstract Using the CELLO detector at PETRA a search has been made for excited leptons by studying e + e − interactions which yield l + l − γγ, l + l − γ and γγ final states, where l =e,μ or τ . Good agreement with QED is observed and new limits are set on e ∗ , μ ∗ , and τ ∗ production.

Limits on spin 0 bosons in

Abstract We have studied the reactions e + e − → e + e − , e + e − → γγ , e + e − → μ + μ − , and e + e − → τ + τ − in the centre-of-mass (CM) energy range from 39.8 to 45.2 GeV using the CELLO detector at PETRA. Upper limits on the partial widths for new spin 0 bosons with masses both within and above the energy range covered are determined. No evidence for contributions of such new particles has been observed up to the highest PETRA energies in a model independent way. Under the assumptions of recently suggested models relating the existence of spin 0 bosons to the radiative width Γ τ of the Z 0 we exclude such bosons at the 95% confidence level for masses below the Z 0 -mass if Γ τ > 20 MeV.

e^+e^-

We have determined the cross section for γγ→π+π+π−π− in a way free of assumptions about the relative contributions fromρ0ρ0,ρ02π and 4π (uncorrelated phase space). We find a sharp onset above threshold and a rather high cross section of about 200 nb aroundWγγ=1.5 GeV which consists to about 40% ofρ0ρ0 production with sizeable contributions fromρ02π and 4π (PS). The total cross section as well as theρ0ρ0 content fall rather fast at higher c.m. energies. Attempts to explain this behaviour in terms of production of known resonances are not successful so far. The angular distributions do not show any significant structure pointing to resonance formation in the 4π-system. Only theρ0-meson is observed in the moment analysis. The decay distributions of theρ0 for forward produced rhos are fairly consistent with helicity conservation of the produced rhos in accordance with the VDM picture.