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Khachatryan, V.,Sirunyan, A. M.,Tumasyan, A.,Adam, W.,Bergauer, T.,Dragicevic, M.,Erö,, J.,Fabjan, C.,Friedl, M.,Frü,hwirth, R.,Ghete, V. M.,Hartl, C.,Hö,rmann, N.,Hrubec, J.,Jeitler, M.,K Springer-Verlag 2014 Journal of high energy physics Vol.2014 No.6
<P>Measurements are presented of the t-channel single-top-quark production cross section in proton-proton collisions at root s = 8 TeV. The results are based on a data sample corresponding to an integrated luminosity of 19.7 fb(-1) recorded with the CMS detector at the LHC. The cross section is measured inclusively, as well as separately for top (t) and antitop (t) over bar, in final states with a muon or an electron. The measured inclusive t-channel cross section is sigma(t-ch.) = 83.6 +/- 2.3 (stat.) +/- 7.4 (syst.) pb. The single t and (t) cross sections are measured to be sigma(t-ch.)(t) = 53.8 +/- 1.5 (stat.) +/- 4.4 (syst.) pb and sigma(t-ch.)(t) over bar = 27.6 +/- 1.3 (stat.) +/- 3.7 (syst.) pb, respectively. The measured ratio of cross sections is Rt-ch. = sigma(t-ch.)(t)/sigma(t-ch.)(t) over bar = 1.95 +/- 0.10 (stat.) +/- 0.19 (syst.), in agreement with the standard model prediction. The modulus of the Cabibbo-Kobayashi-Maskawa matrix element V-tb is extracted and, in combination with a previous CMS result at root s = 7 TeV, a value vertical bar V-tb vertical bar = 0.998 +/- 0.038 (exp.) +/- 0.016 (theo.) is obtained.</P>
Khachatryan, V.,Sirunyan, A. M.,Tumasyan, A.,Adam, W.,Asilar, E.,Bergauer, T.,Brandstetter, J.,Brondolin, E.,Dragicevic, M.,Erö,, J.,Flechl, M.,Friedl, M.,Frü,hwirth, R.,Ghete, V. M.,Hartl, C. Institute of Physics Pub 2017 The journal of high energy physics Vol.2017 No.3
<P>The results of a first search for CP violation in the production and decay of top quark-antiquark (t (t) over bar) pairs are presented. The search is based on asymmetries in T-odd, triple-product correlation observables, where T is the time-reversal operator. The analysis uses a sample of proton-proton collisions at root s = 8 TeV collected by the CMS experiment, corresponding to an integrated luminosity of 19.7fb(-1). Events are selected having one electron or muon and at least four jets. The T-odd observables are measured using four-momentum vectors associated with t (t) over bar production and decay. The measured asymmetries exhibit no evidence for CP-violating effects, consistent with the expectation from the standard model.</P>
Khachatryan, V.,Sirunyan, A. M.,Tumasyan, A.,Adam, W.,Asilar, E.,Bergauer, T.,Brandstetter, J.,Brondolin, E.,Dragicevic, M.,Erö,, J.,Flechl, M.,Friedl, M.,Frü,hwirth, R.,Ghete, V. M.,Hartl, C. Institute of Physics Pub 2017 The journal of high energy physics Vol.2017 No.2
<P>Single top quark events produced in the t channel are used to set limits on anomalous Wtb couplings and to search for top quark flavour-changing neutral current (FCNC) interactions. The data taken with the CMS detector at the LHC in proton-proton collisions at and 8 TeV correspond to integrated luminosities of 5.0 and 19.7 fb(-1), respectively. The analysis is performed using events with one muon and two or three jets. A Bayesian neural network technique is used to discriminate between the signal and backgrounds, which are observed to be consistent with the standard model prediction. The 95% confidence level (CL) exclusion limits on anomalous right-handed vector, and left- and right-handed tensor Wtb couplings are measured to be vertical bar f (V) (R) vertical bar < 0.16,aEuro,vertical bar f (T) (L) vertical bar < 0.057, and - 0.049 < f (T) (R) < 0.048, respectively. For the FCNC couplings kappa (tug) and kappa (tcg), the 95% CL upper limits on coupling strengths are vertical bar kappa (tug)vertical bar/I > < 4.1 x 10(- 3) TeV-1 and vertical bar kappa (tcg)vertical bar/Lambda < 1.8 x 10(- 2) TeV-1, where I > is the scale for new physics, and correspond to upper limits on the branching fractions of 2.0 x 10(-5) and 4.1 x 10(-4) for the decays t -> ug and t -> cg, respectively.</P>
A New MHD-assisted Stokes Inversion Technique
Riethmü,ller, T. L.,Solanki, S. K.,Barthol, P.,Gandorfer, A.,Gizon, L.,Hirzberger, J.,Noort, M. van,Rodrí,guez, J. Blanco,Iniesta, J. C. Del Toro,Suá,rez, D. Orozco,Schmidt, W.,Pillet, American Astronomical Society 2017 The Astrophysical journal Supplement series Vol.229 No.1
<P>We present a new method of Stokes inversion of spectropolarimetric data and evaluate it by taking the example of a SUNRISE/IMaX observation. An archive of synthetic Stokes profiles is obtained by the spectral synthesis of stateof- the-art magnetohydrodynamics (MHD) simulations and a realistic degradation to the level of the observed data. The definition of a merit function allows the archive to be searched for the synthetic Stokes profiles that best match the observed profiles. In contrast to traditional Stokes inversion codes, which solve the Unno-Rachkovsky equations for the polarized radiative transfer numerically and fit the Stokes profiles iteratively, the new technique provides the full set of atmospheric parameters. This gives us the ability to start an MHD simulation that takes the inversion result as an initial condition. After a relaxation process of half an hour solar time we obtain physically consistent MHD data sets with a target similar to the observation. The new MHD simulation is used to repeat the method in a second iteration, which further improves the match between observation and simulation, resulting in a factor of 2.2 lower mean chi(2) value. One advantage of the new technique is that it provides the physical parameters on a geometrical height scale. It constitutes a first step toward inversions that give results consistent with the MHD equations.</P>