Search results for "Vector"
showing 10 items of 2660 documents
Review of single vector boson production in pp collisions at $$\sqrt{s} = 7$$ s = 7 TeV
2014
This review summarises the main results on the production of single vector bosons in the Standard Model, both inclusively and in association with light- and heavy-flavour jets, at the Large Hadron Collider in proton–proton collisions at a centre-of-mass energy of $$7\,{\mathrm {\ TeV}}$$ . The general purpose detectors at this collider, ATLAS and CMS, each recorded an integrated luminosity of $${\approx } 40\,\mathrm{pb^{-1}}$$ and $$5\,\mathrm{fb^{-1}}$$ in the years 2010 and 2011, respectively. The corresponding data offer the unique possibility to precisely study the properties of the production of heavy vector bosons in a new energy regime. The accurate understanding of the Standard Mod…
Measurement of OZI rule violation and spin alignment inϕandωproduction at COMPASS
2012
The COMPASS collaboration at CERN dedicated the 2008 and 2009 run time to hadron spectroscopy measurements with emphasis on the mesonic sector. At 190 GeV/c beam momentum, diffractive and double-Reggeon/Pomeron production mechanisms contribute. Studying vector meson production allows to explore this relatively unknown transition domain. We present results on the ratio of production yields for p p → (1020) p p ϕ and p p → p p ω (782) and its xF dependence where we find an OZI rule violation in the order of a factor of 3. In addition, the spin alignment of ω and ϕ as a function of xF is investigated.
Measurements of charm mixing and CP violation using D0→K±π∓ decays
2017
Measurements of charm mixing and CP violation parameters from the decay-time-dependent ratio of D0→K+π− to D0→K−π+ decay rates and the charge-conjugate ratio are reported. The analysis uses B¯¯¯¯→D∗+μ−X, and charge-conjugate decays, where D∗+→D0π+, and D0→K∓π±. The pp collision data are recorded by the LHCb experiment at center-of-mass energies s√ = 7 and 8 TeV, corresponding to an integrated luminosity of 3 fb−1. The data are analyzed under three hypotheses: (i) mixing assuming CP symmetry, (ii) mixing assuming no direct CP violation in the Cabibbo-favored or doubly Cabibbo-suppressed decay amplitudes, and (iii) mixing allowing either direct CP violation and/or CP violation in the superpos…
Semileptonic decays of B(*) , D(*) into νl and pseudoscalar or vector mesons
2018
We perform a study of the ${B}^{(*)}$, ${D}^{(*)}$ semileptonic decays, using a different method than in conventional approaches, where the matrix elements of the weak operators are evaluated and a detailed spin-angular momentum algebra is performed to obtain very simple expressions at the end for the different decay modes. Using only one experimental decay rate in the $B$ or $D$ sectors, the rates for the rest of decay modes are predicted and they are in good agreement with experiment. Some discrepancies are observed in the $\ensuremath{\tau}$ decay mode for which we find an explanation. We perform evaluations for ${B}^{*}$ and ${D}^{*}$ decay rates that can be used in future measurements,…
Chiral symmetry amplitudes in the S-wave isoscalar and isovector channels and the σ, f[sub 0](980), a[sub 0](980) scalar mesons
1998
We use a nonperturbative approach which combines coupled channel Lippmann Schwinger equations with meson-meson potentials provided by the lowest order chiral Lagrangian. By means of one parameter, a cut off in the momentum of the loop integrals, which results of the order of 1 GeV, we obtain singularities in the S-wave amplitudes corresponding to the σ, f0 and a0 resonances. The ππ→ππ, ππ→KK phase shifts and inelasticities in the T=0 scalar channel are well reproduced as well as the π0η and KK mass distributions in the T=1 channel. Furthermore, the total and partial decay widths of the f0 and a0 resonances are properly reproduced. The results seem to indicate that chiral symmetry constraint…
Observation of the Semileptonic D+ Decay into the K¯1(1270)0 Axial-Vector Meson
2019
By analyzing a 2.93 fb(-1) data sample of e(+)e(-) collisions, recorded at a center-of-mass energy of 3.773 GeV with the BESIII detector operated at the BEPCII collider, we report the first observa ...
Working group on goldstone boson production and decay
2008
This is the summary of the working group on Goldstone Boson Production and Decay of the Chiral Dynamics Workshop in Mainz, September 1–5, 1997. For the production aspects we discuss π0 and η production in nucleon-nucleon collisions and the behaviour of hadrons in various sum rules. For the decays we present a discussion on various K, η and π decay channels. Other aspects discussed are a new treatment of meson-meson scattering, the light-by-light contribution to the muon anomalous magnetic moment and progress in various aspects of the p 6 generating functional in the mesonic sector.
Search for a Heavy Particle Decaying into an Electron and a Muon with the ATLAS Detector ins=7 TeVppcollisions at the LHC
2011
This Letter presents the first search for a heavy particle decaying into an e(+/-)mu(-/+) final state in root s = 7 TeV pp collisions at the LHC. The data were recorded by the ATLAS detector during 2010 and correspond to a total integrated luminosity of 35 pb(-1). No excess above the standard model background expectation is observed. Exclusions at 95% confidence level are placed on two representative models. In an R-parity violating supersymmetric model, tau sneutrinos with a mass below 0.75 TeV are excluded, assuming all R-parity violating couplings are zero except lambda(311)' = 0.11 and lambda(312) = 0.07. In a lepton flavor violating model, a Z'-like vector boson with masses of 0.70-1.0…
Search for a Heavy Neutral Particle Decaying toeμ,eτ, orμτinppCollisions ats=8 TeVwith the ATLAS Detector
2015
This Letter presents a search for a heavy neutral particle decaying into an opposite-sign different-flavor dilepton pair, e(+/-) mu(-/+), e(+/-) tau(-/+), or mu(+/-) tau(-/+) using 20.3 fb(-1) of pp collision data at root s = 8 TeV collected by the ATLAS detector at the LHC. The numbers of observed candidate events are compatible with the standard model expectations. Limits are set on the cross section of new phenomena in two scenarios: the production of (nu) over tilde (tau) in R-parity-violating supersymmetric models and the production of a lepton-flavor-violating Z' vector boson.