| Datum |
Publikation |
Thema |
Herausgeber |
Co-Autoren |
Art |
Stadt |
|
03
.
2018
|
Search for additional neutral MSSM Higgs bosons in the tau tau final state in proton-ptoron collisions at √s=13 TeV |
A search is presented for additional neutral Higgs bosons in the ττ final state in proton-proton collisions at the LHC. The search is performed in the context of the minimal supersymmetric extension of the standard model (MSSM), using the data collected with the CMS detector in 2016 at a center-of-mass energy of 13 TeV, corresponding to an integrated luminosity of 35.9 fb−1. To enhance the sensitivity to neutral MSSM Higgs bosons, the search includes production of the Higgs boson in association with b quarks. No significant deviation above the expected background is observed. Model-independent limits at 95% confidence level (CL) are set on the product of the branching fraction for the decay into τ leptons and the cross section for the production via gluon fusion or in association with b quarks. These limits range from 18 pb at 90 GeV to 3.5 fb at 3.2 TeV for gluon fusion and from 15 pb (at 90 GeV) to 2.5 fb (at 3.2 TeV) for production in association with b quarks, assuming a narrow width resonance. In the mmod+h scenario these limits translate into a 95% CL exclusion of tanβ> 6 for neutral Higgs boson masses below 250 GeV, where tanβ is the ratio of the vacuum expectation values of the neutral components of the two Higgs doublets. The 95% CL exclusion contour reaches 1.6 TeV for tanβ= 60. |
JHEP 09 (2018) 007 |
CMs Collaboration |
Fachzeitschrift |
|
|
03
.
2018
|
Identifying the relevant dependencies of the neural network response on characteristics of the input space |
The relation between the input and output spaces of neural networks (NNs) is investigated to identify those characteristics of the input space that have a large influence on the output for a given task. For this purpose, the NN function is decomposed into a Taylor expansion in each element of the input space. The Taylor coefficients contain information about the sensitivity of the NN response to the inputs. A metric is introduced that allows for the identification of the characteristics that mostly determine the performance of the NN in solving a given task. Finally, the capability of this metric to analyze the performance of the NN is evaluated based on a task common to data analyses in high-energy particle physics experiments. |
Comput. Sotw. Big Sci. 2 (2018) 5 |
Stefan Wunsch, Raphael Friese, Günter Quast |
Fachzeitschrift |
|
|
01
.
2018
|
Measurement of the Z to tau tau cross section in pp collisions at √s=13 TeV and validation of tau lepton analysis techniques |
A measurement is presented of the Z/γ∗→ττ cross section in pp collisions at s√= 13 TeV, using data recorded by the CMS experiment at the LHC, corresponding to an integrated luminosity of 2.3 fb−1. The product of the inclusive cross section and branching fraction is measured to be σ(pp→Z/γ∗+X)B(Z/γ∗→ττ)= 1848 ± 12 (stat) ± 67 (syst+lumi) pb, in agreement with the standard model expectation, computed at next-to-next-to-leading order accuracy in perturbative quantum chromodynamics. The measurement is used to validate new analysis techniques relevant for future measurements of τ lepton production. The measurement also provides the reconstruction efficiency and energy scale for τ decays to hadrons+ντ final states, determined with respective relative uncertainties of 2.2% and 0.9%. |
Eur. Phys. J. C78 (2018) 708 |
CMS Collaboration |
Fachzeitschrift |
|
|
08
.
2017
|
Observation of the Higgs boson decay to a pair of tau leptons |
A measurement of the coupling strength of the Higgs boson to tau leptons is performed using events recorded in proton-proton collisions by the CMS experiment at the LHC in 2016 at a center-of-mass energy of 13 TeV. The data set corresponds to an integrated luminosity of 35.9 inverse femtobarns. The H to tau tau signal is established with a significance of 4.9 standard deviations, to be compared to an expected significance of 4.7 standard deviations. The best fit of the product of the observed H to tau tau signal production cross section and branching fraction is 1.09+0.27-0.26 times the standard model expectation. The combination with the corresponding measurement performed with data collected by the CMS experiment at center-of-mass energies of 7 and 8 TeV leads to an observed significance of 5.9 standard deviations, equal to the expected significance. This is the first observation of Higgs boson decays to tau leptons by a single experiment. |
Phys. Lett. B779 (2018) 283 |
CMS Collaboration |
Fachzeitschrift |
|
|
05
.
2015
|
The Higgs Boson Discovery at the Large Hadron Collider |
This book provides a comprehensive overview of the field of Higgs boson physics. It offers the first in-depth review of the complete results in connection with the discovery of the Higgs boson at CERN’s Large Hadron Collider and based on the full dataset for the years 2011 to 2012. The fundamental concepts and principles of Higgs physics are introduced and the important searches prior to the advent of the Large Hadron Collider are briefly summarized.
Lastly, the discovery and first mensuration of the observed particle in the course of the CMS experiment are discussed in detail and compared to the results obtained in the ATLAS experiment. |
Springer Tracts of modern Physics Volume 264 (2015) |
|
Buch |
|
|
08
.
2014
|
Search for neutral MSSM Higgs bosons decaying to a pair of tau leptons in pp collisions |
A search for neutral Higgs bosons in the minimal supersymmetric extension of the standard model (MSSM) decaying to tau-lepton pairs in pp collisions is performed, using events recorded by the CMS experiment at the LHC. The dataset corresponds to an integrated luminosity of 24.6 inverse femtobarns, with 4.9 inverse femtobarns at 7 TeV and 19.7 inverse femtobarns at 8 TeV. To enhance the sensitivity to neutral MSSM Higgs bosons, the search includes the case where the Higgs boson is produced in association with a b-quark jet. No excess is observed in the tau-lepton-pair invariant mass spectrum. Exclusion limits are presented in the MSSM parameter space for different benchmark scenarios, m[h,max}, m[h,mod+], m[h,mod-], light-stop, light-stau, tau-phobic, and low-m[H]. Upper limits on the cross section times branching fraction for gluon fusion and b-quark associated Higgs boson production are also given. |
JHEP 10 (2014) 160 |
CMS Collaboration |
Fachzeitschrift |
|
|
01
.
2014
|
Evidence for the 125 GeV Higgs boson decaying to a pair of tau leptons |
A search for a standard model Higgs boson decaying into a pair of tau leptons is performed using events recorded by the CMS experiment at the LHC in 2011 and 2012. The dataset corresponds to an integrated luminosity of 4.9 inverse femtobarns at a centre-of-mass energy of 7 TeV and 19.7 inverse femtobarns at 8 TeV. Each tau lepton decays hadronically or leptonically to an electron or a muon, leading to six different final states for the tau-lepton pair, all considered in this analysis. An excess of events is observed over the expected background contributions, with a local significance larger than 3 standard deviations for m[H] values between 115 and 130 GeV. The best fit of the observed H to tau tau signal cross section for m[H] = 125 GeV is 0.78 +- 0.27 times the standard model expectation. These observations constitute evidence for the 125 GeV Higgs boson decaying to a pair of tau leptons. |
JHEP 05 (2014) 104 |
CMS Collaboration |
Fachzeitschrift |
|
|
01
.
2014
|
Evidence for the direct decay of the 125 GeV Higgs boson to fermions |
The discovery of a new boson with a mass of approximately 125 GeV in 2012 at the LHC has heralded a new era in understanding the nature of electroweak symmetry breaking and possibly completing the standard model of particle physics. Since the first observation in decays to gamma gamma, WW, and ZZ boson pairs, an extensive set of measurements of the mass and couplings to W and Z bosons, as well as multiple tests of the spin-parity quantum numbers, have revealed that the properties of the new boson are consistent with those of the long-sought agent responsible for electroweak symmetry breaking. An important open question is whether the new particle also couples to fermions, and in particular to down-type fermions, since the current measurements mainly constrain the couplings to the up-type top quark. Determination of the couplings to down-type fermions requires direct measurement of the corresponding Higgs boson decays, as recently reported by the CMS experiment in the study of Higgs decays to bottom quarks and tau leptons. In this paper we report the combination of these two channels which results, for the first time, in strong evidence for the direct coupling of the 125 GeV Higgs boson to down-type fermions, with an observed significance of 3.8 standard deviations, when 4.4 are expected. |
Nature Physics 10 (2014) 557 |
CMS Collaboration |
Fachzeitschrift |
|
|
07
.
2012
|
Observation of a new boson at a mass of 125 GeV with the CMS experiment at the LHC |
Results are presented from searches for the standard model Higgs boson in proton-proton collisions at sqrt(s) = 7 and 8 TeV in the Compact Muon Solenoid experiment at the LHC, using data samples corresponding to integrated luminosities of up to 5.1 inverse femtobarns at 7 TeV and 5.3 inverse femtobarns at 8 TeV. The search is performed in five decay modes: gamma gamma, ZZ, WW, tau tau, and b b-bar. An excess of events is observed above the expected background, with a local significance of 5.0 standard deviations, at a mass near 125 GeV, signalling the production of a new particle. The expected significance for a standard model Higgs boson of that mass is 5.8 standard deviations. The excess is most significant in the two decay modes with the best mass resolution, gamma gamma and ZZ; a fit to these signals gives a mass of 125.3 +/- 0.4 (stat.) +/- 0.5 (syst.) GeV. The decay to two photons indicates that the new particle is a boson with spin different from one. |
Phys. Lett. B 716 (2012) 30 |
CMS Collaboration |
Fachzeitschrift |
|
|
02
.
2012
|
Search for neutral Higgs bosons decaying to tau pairs in pp collisions at sqrt(s) = 7 TeV |
A search for neutral Higgs bosons decaying to tau pairs at a center-of-mass energy of 7 TeV is performed using a dataset corresponding to an integrated luminosity of 4.6 inverse femtobarns recorded by the CMS experiment at the LHC. The search is sensitive to both the standard model Higgs boson and to the neutral Higgs bosons predicted by the minimal supersymmetric extension of the standard model (MSSM). No excess of events is observed in the tau-pair invariant-mass spectrum. For a standard model Higgs boson in the mass range of 110-145 GeV upper limits at 95% confidence level (CL) on the production cross section are determined. We exclude a Higgs boson with m(H) = 115 GeV with a production cross section 3.2 times of that predicted by the standard model. In the MSSM, upper limits on the neutral Higgs boson production cross section times branching fraction to tau pairs, as a function of the pseudoscalar Higgs boson mass, m(A), sets stringent new bounds in the parameter space, excluding at 95% CL values of tan(beta) as low as 7.1 at m(A) = 160 GeV in the m[h](max) benchmark scenario. |
Phys. Lett. B 713 (2012) 68 |
CMS Collaboration |
Fachzeitschrift |
|
