A search is conducted for a low-mass charged Higgs boson produced in a top quark decay and subsequently decaying into a charm and a strange quark. The data sample was recorded in proton-proton collisions at $\\sqrt{s}=$ 13 TeV by the CMS experiment at the LHC and corresponds to an integrated luminosity of 35.9 fb$^{-1}$. The search is performed in the process of top quark pair production, where one top quark decays to a bottom quark and a charged Higgs boson, and the other to a bottom quark and a W boson. With the W boson decaying to a charged lepton (electron or muon) and a neutrino, the final state comprises an isolated lepton, missing transverse momentum, and at least four jets, of which two are tagged as b jets. To enhance the search sensitivity, one of the jets originating from the charged Higgs boson is required to satisfy a charm tagging selection. No significant excess beyond standard model predictions is found in the dijet invariant mass distribution. An upper limit in the range 1.68-0.25% is set on the branching fraction of the top quark decay to the charged Higgs boson and bottom quark for a charged Higgs boson mass between 80 and 160 GeV.

Article history: Received 30 January 2015 Received in revised form 1 July 2015 Accepted 16 July 2015 Available online 22 July 2015 Editor: M. Doser

Article history: Received 7 July 2013 Received in revised form 20 November 2013 Accepted 2 December 2013 Available online 6 December 2013 Editor: M. Doser

In this note the results from the hit reconstruction and local track reconstruction inside two DT muon barrel chambers exposed to a muon testbeam in October 2004 are compared with the output from the full simulation based on the CMS simulation program, OSCAR, and on the reconstruction package ORCA, currently used for the studies performed for the CMS Physics TDR.

The performance of the Local AutoTrigger of the Muon Barrel Drift Tube Chambers of the CMS experiment has been studied with cosmic rays with a fully equipped chamber at the Laboratori Nazionali di Legnaro (LNL). Cosmic ray results show that the possibility to fully check one or more chambers with respect to uniformity of wire behavior (efficiency, drift velocity) and trigger performance, without any external trigger, is quite high. The purity of the trigger has been measured to be better than 99% when a high quality trigger is required. * anna.meneguzzo@pd.infn.it CMS Internal Note The content of this note is intended for CMS internal use and distribution only

This document contains an updated 1 analysis of the data collected during the 2003 test beam. Selection of the single muon sample was refined and finalized. New efficiency calculations were therefore performed, although minor differences were found. Data collected in the various tested configurations were analyzed and the incidence of the parameters modification on the trigger performance in terms of efficiency and noise was evaluated.

A prototype of the CMS Barrel Muon Detector incorporating all the features of the final chambers was built using the mass production assembly procedures and tools. The performance of this prototype was studied in a muon test beam at CERN and the results obtained are presented in this paper.

A sample of ASIC prototypes of the first-level trigger front-end device for the muon barrel drift chambers of CMS was tested on a full size chamber prototype. Tests were performed at several incident angles on cosmic rays and at normal incidence using a muon beam. The chamber was irradiated using a 137 C s gamma source to simulate the LHC radiation environment. The performance of the tested prototypes with respect to efficiency, resolution and noise issues is reported.

The drift chambers in the barrel region of the CMS detector are exposed to magnetic stray fields. To study the performance of the muon reconstruction and the drift time-based muon trigger, prototypes were tested under the expected magnetic field conditions at the H2 test facility at CERN. The results indicate that the overall chamber performance will not be affected. Only the bunch crossing identification capability in the small region near η=1.1, corresponding to the border of the solid angle region covered by the barrel, will be weakened.

The development of the barrel drift chambers for the CMS muon detector at the CERN Large Hadron Collider is supported by a variety of simulation calculations, based on the GARFIELD drift chamber simulation program and the GEANT detector simulation package. This study surveys the results influencing the actual chamber design. The dependence of the drift cell performance on shape and position of the cell electrodes as well as on the mechanical tolerances is shown. The results obtained for space-time relation and spatial resolution are in good agreement to test beam measurements on prototypes.

The momentum and angular distributions of punchthrough muons have been measured after a 10 λ calorimeter using an iron toroid magnet with 1.5 T as spectrometer. The calorimeter was inside a variable magnetic field of 0 to 3 T. The incident momentum of the π− beam ranged from 20 to 300 GeV/c. Measurements were also done at some beam momenta for π+, K+ and p. The results are compared with Monte Carlo predictions. A parameterization for the momentum spectrum of punchthrough muons was derived from the data.

Three simplified prototypes of the first-level trigger front-end device for the muon barrel drift chambers of CMS were tested on a chamber prototype. Tests were performed at several incidence angles of a muon beam and with different magnetic field configurations. The recorded drift times were also used to test a full software model reproducing the actual algorithm applied in the final ASIC being produced. The efficiency performance of this software model and of the tested prototype are presented in this paper.

The total punchthrough probability of showers produced by negative pions, positive pions, positive kaons and protons, has been measured as a function of depth in an absorber in a magnetic field ranging from 0 to 3 Tesla.The incident particle momentum varied from 10 to 300 GeV/c.The lateral shower development and particle multiplicity at several absorber depths have been determined.The measurements are compared with the predictions of Monte Carlo simulation programs.

The experiments at the planned 14 TeV proton-proton collider LHC will need a good identification and measurement of muons with energies of up to about 800 GeV. The production of electromagnetic secondaries by muons of energy from 10 to 300 GeV has been measured at the RD5 experiment at CERN using various detector types proposed for LHC experiments. It is demonstrated that the detectors can recognize the presence of individual hits from em secondaries, and that the muon measurement would be seriously compromised if these hits are not suppressed.

The performance of a small prototype chamber of the baseline project for the muon barrel detector for CMS has been studied in a muon beam. Its efficiency with different gases and wire diameters, the trigger possibilities and the response in presence of a large number of electromagnetic secondaries associated to the muon are evaluated. The results are compared with a full Monte Carlo simulation.

A novel muon detector concept for LHC was studied in a test beam. The application of mean-timer technique to arrays of drift tubes provides the space and time resolution needed for first level trigger and track reconstruction using only the drift time information. A complete study of the performance of this new detector was done.

The s dependence of the electromagnetic proton form factors in the time-like region has been determined from the threshold (s = 4Mp2) up to s = 4.2 GeV2. Data were collected in a dedicated experiment performed at the LEAR antiproton ring at CERN, increasing by one order of magnitude the available statistics. Total and differential cross section of the pp → e−e+ reaction have been measured. The electric and magnetic form factors are found to have comparable value. The observed form factor shows a clear steep s dependence close to the threshold.

A novel method was developed to obtain precise timing of muon hits in drift tubes at the first trigger level, and hence to associate a detected muon with the bunch crossing in which it originated. A very good time resolution of approximately 2 ns was obtained. Some other topics related to muon detection were investigated.

The total punchthrough probability of showers produced by negatively charged pions of momenta 30, 40, 50, 75, 100, 200 and 300 GeV/c, has been measured in the RD5 experiment at CERN using a toroidal spectrometer. The range of the measurement extends to 5.3 m of equivalent iron. Our results have been obtained by two different analysis methods and are compared with the resutls of a previous experiment.