Search for the standard model Higgs boson in associated WH production in the eμτ and μμτ final states

The Standard Model (SM) Higgs boson is mainly produced from gluon-gluon and vector boson fusion at LHC. The associated production with vector bosons, although with a lower cross section, can be also considered a sensitive channel because a significant background rejection can be achieved using the presence of highly energetic charged leptons coming from the decays of W/Z. In the lightmass region, the SM Higgs boson decay into τ -lepton pairs has the second highest branching ratio, after the decay into b¯ b. For these reasons, a search for WH process is performed, in which the W boson decays into muon or electron, and the Higgs boson into a τ -pair, in which one τ decays into leptons and the other hadronically (τh). The analysis is based on data collected with the CMS detector during 2011, corresponding to an integrated luminosity of 4.7 fb−1 at a center-of-mass energy of 7TeV at LHC. The results are consistent with the expected SM background, so upper limits are set at 95% CL for the SM Higgs boson production cross section. The method used to estimate the background from data, is based on the fake-rate technique (CMS Physics Analysis Summary, CMS PAS HIG-12-006 (2012))

Search for the standard model Higgs boson decaying into tau pairs produced in association with a W or Z boson

A search of the Standard Model (SM) Higgs boson production in association with a vector boson, W or Z, is performed at LHC, using data collected with the CMS detector during 2011 and 2012, corresponding to a total integrated luminosity of 24.5 fb−1. The associated production represents an interesting channel for the low-mass Higgs boson search, thanks to the presence of highly energetic leptons coming from W and Z decays which suppress the most relevant SM backgrounds. The Higgs decay search is performed in the di-τ decay mode, in which each τ can decay into an electron, a muon or hadronically (τh) and a neutrino. The WH channel has three leptons in the final state, with W decaying into electron or muon and a neutrino; instead the ZH channel is performed in a four leptons final state, where the Z decays into a pair of electrons or muons. The data analysed are compatible with the SM expected background, and no significant excess is observed

Implementation of an Optimal First-Order Method for Strongly Convex Total Variation Regularization

We present a practical implementation of an optimal first-order method, due to Nesterov, for large-scale total variation regularization in tomographic reconstruction, image deblurring, etc. The algorithm applies to $\mu$-strongly convex objective functions with $L$-Lipschitz continuous gradient. In the framework of Nesterov both $\mu$ and $L$ are assumed known -- an assumption that is seldom satisfied in practice. We propose to incorporate mechanisms to estimate locally sufficient $\mu$ and $L$ during the iterations. The mechanisms also allow for the application to non-strongly convex functions. We discuss the iteration complexity of several first-order methods, including the proposed algorithm, and we use a 3D tomography problem to compare the performance of these methods. The results show that for ill-conditioned problems solved to high accuracy, the proposed method significantly outperforms state-of-the-art first-order methods, as also suggested by theoretical results.Comment: 23 pages, 4 figure

Constraints on the χ_(c1) versus χ_(c2) polarizations in proton-proton collisions at √s = 8 TeV

The polarizations of promptly produced χ_(c1) and χ_(c2) mesons are studied using data collected by the CMS experiment at the LHC, in proton-proton collisions at √s=8  TeV. The χ_c states are reconstructed via their radiative decays χ_c → J/ψγ, with the photons being measured through conversions to e⁺e⁻, which allows the two states to be well resolved. The polarizations are measured in the helicity frame, through the analysis of the χ_(c2) to χ_(c1) yield ratio as a function of the polar or azimuthal angle of the positive muon emitted in the J/ψ → μ⁺μ⁻ decay, in three bins of J/ψ transverse momentum. While no differences are seen between the two states in terms of azimuthal decay angle distributions, they are observed to have significantly different polar anisotropies. The measurement favors a scenario where at least one of the two states is strongly polarized along the helicity quantization axis, in agreement with nonrelativistic quantum chromodynamics predictions. This is the first measurement of significantly polarized quarkonia produced at high transverse momentum