Search results for "gauge boson"
showing 10 items of 171 documents
Photoproduction of thef2′(1525), a2(1320), andK2*(1430)
2016
Assuming that the ${f}_{2}^{\ensuremath{'}}(1525), {a}_{2}(1320)$, and ${K}_{2}^{*}(1430)$ resonances are dynamically generated states from vector-meson--vector-meson interactions in the $s$-wave with spin $S=2$, we study the $\ensuremath{\gamma}p\ensuremath{\rightarrow}{f}_{2}^{\ensuremath{'}}(1525)p, \ensuremath{\gamma}p\ensuremath{\rightarrow}{a}_{2}^{0}(1320)p$, and $\ensuremath{\gamma}p\ensuremath{\rightarrow}{K}_{2}^{*}(1430)\mathrm{\ensuremath{\Lambda}}(\mathrm{\ensuremath{\Sigma}})$ reactions. These reactions proceed in the following way: the incoming photon first mutates into a ${\ensuremath{\rho}}^{0}, \ensuremath{\omega}$, or $\ensuremath{\phi}$ meson via vector-meson dominance, …
Double Copies of Fermions as Matter that Interacts Only Gravitationally
2016
Inspired by the recent progress in the field of scattering amplitudes, we discuss hypothetical particles which can be characterized as the double copies of fermions-in the same way gravitons can be viewed as double copies of gauge bosons. As the gravitons, these hypothetical particles interact only through gravitational interactions. We present two equivalent methods for the computation of the relevant scattering amplitudes. The hypothetical particles can be massive and nonrelativistic.
New Strong Interactions: From QCD to LHC
2006
The concept of strong interactions need not be limited to the sector of physics taken by QCD. While this domain is investigated by RHIC, LHC will be able to probe potential new strong interactions simultaneously: Finding the precise mechanism for electroweak symmetry breaking is one of the prime problems of physics. Intricately linked to this point is the question after the true nature or even the existence of the Higgs boson. Here, we present stronly interacting theories providing an explanation for the hierarchy problem and leading to a light composite Higgs boson, favoured by experimental data. Our variation of the standard model is consistent with precision data. We achieve this accorda…
A Comment on form-factor mass singularities in flavor changing neutral currents
1991
Flavor-changing effective verticesq l q h V 0, whereV 0 represents a neutral gauge boson (γ,Z 0,g), involving a heavy external quark, are discussed within the standard model at one-loop level and second-order approximation in external momenta and masses: the logarithmic singular terms in the form factors at vanishing mass of the internal quark in the loop have to be replaced by pieces coming from next order in external momenta. Implications in theb→d+X penguin transitions are commented.
Search for heavy vector-like quarks coupling to light quarks in proton–proton collisions at s=7 TeV with the ATLAS detector
2012
This letter presents a search for singly produced vector-like quarks, Q, coupling to light quarks, q. The search is sensitive to both charged current (CC) and neutral current (NC) processes, p p --> Q q --> W q q' and p p --> Q q --> Z q q' with a leptonic decay of the vector gauge boson. In 1.04/fb of data taken in 2011 by the ATLAS experiment at a center-of-mass energy sqrt(s) = 7 TeV, no evidence of such heavy vector-like quarks is observed above the expected Standard Model background. Limits on the heavy vector-like quark production cross section times branching ratio as a function of mass m_Q are obtained. For a coupling kappa_(qQ) = v/m_Q, where v is the Higgs vacuum expectation value…
Spontaneous CP violation in the left-right model and the kaon system
1996
A left-right model with spontaneous $CP$ breakdown, consistent with the particle physics phenomenology, is presented. Constraints on free parameters of the model: mass of the new right handed gauge boson $M_2$ and ratio $r$ of the two vacuum expectation values of the bidoublet, are found from the measurement of $\epsilon$ in the kaon system. For most of the parameter space, $M_2$ is restricted to be below 10 TeV. Higher masses can be achieved only by fine tuning of Kobayashi-Maskawa matrix elements, quark masses, $r$ and the phase $\alpha$ which is the unique source of $CP$-violation in the model. Large number of combinations of signs of quark masses, which are observables of the model, are…
Search for W′→tb resonances with left- and right-handed couplings to fermions
2011
We present a search for the production of a heavy gauge boson, W', that decays to third-generation quarks, by the D0 Collaboration in ppbar collisions at sqrt(s)= 1.96 TeV. We set 95% confidence level upper limits on the production cross section times branching fraction. For the first time, we set limits for arbitrary combinations of left- and right-handed couplings of the W' boson to fermions. For couplings with the same strength as the standard model W boson, we set the following limits for M(W') > m(nu_R): M(W')>863 GeV for purely left-handed couplings, M(W')>885 GeV for purely right-handed couplings, and M(W')>916 GeV if both left- and right-handed couplings are present. The limit for r…
Constraints on additionalZ′gauge bosons from a precise measurement of theZmass
1990
We analyze the constraints on the mass and mixing of superstring-inspired E{sub 6} {ital Z}{prime} neutral gauge boson that follow from the recent precise {ital Z} mass measurements and show that they depend very sensitively on the assumed value of the {ital W} mass and also, to a lesser extent, on the top-quark mass.
Search for Axionlike Particles Produced in e+e− Collisions at Belle II
2020
We present a search for the direct production of a light pseudoscalar a decaying into two photons with the Belle II detector at the SuperKEKB collider. We search for the process e+e-→γa, a→γγ in the mass range 0.2<ma<9.7 GeV/c2 using data corresponding to an integrated luminosity of (445±3) pb-1. Light pseudoscalars interacting predominantly with standard model gauge bosons (so-called axionlike particles or ALPs) are frequently postulated in extensions of the standard model. We find no evidence for ALPs and set 95% confidence level upper limits on the coupling strength gaγγ of ALPs to photons at the level of 10-3 GeV-1. The limits are the most restrictive to date for 0.2<ma<1 GeV/c2.
Lepton-number violation with quasi-Dirac neutrinos
1983
We investigate lepton-number violation in weak interactions with massive Dirac neutrinos. In the framework of a simple $\mathrm{SU}{(3)}_{L}\ifmmode\times\else\texttimes\fi{}\mathrm{U}(1)$ electroweak model we find that neutrinos naturally acquire only Dirac masses at tree level, and for an odd number of lepton families, one neutrino remains massless. After a spontaneous breakdown of symmetry we find that the SU(2)\ifmmode\times\else\texttimes\fi{}U(1) effective theory has lepton-number-violating currents which couple to the standard gauge bosons. Flavorconserving $|\ensuremath{\Delta}l|=2$ processes such as neutrinoless double-$\ensuremath{\beta}$ decay are forbidden in the simplest model,…