Intermediate vector bosons as unobservable particles.
Intermediate vector bosons as unobservable particles described by renormalizable Lagrangian in indefinite metric space
NUCLEAR PHYSICS↗
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Intermediate vector bosons, SU(3) symmetry and CP violation
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Tomozawa, Y.↗
Adding pseudo-observables to the four-lepton experimentalist’s toolbox
Here, the "golden" channel, in which the newly-discovered Higgs boson decays to four leptons by means of intermediate vector bosons, is important for determining the properties of the Higgs boson and for searching for subtle new physics effects. Different approaches exist for parametrizing the relevant Higgs couplings in this channel; here we relate the use of pseudo-observables to methods based on specifying the most general amplitude or Lagrangian terms for the $HVV$ interactions. We also provide projections for sensitivity in this channel in several novel scenarios, illustrating the use of pseudo-observables, and analyze the role of kinematic distributions and (ratios of) rates in such $H\to4\ell$ studies.
72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
Cosmic ray neutrino tests for heavier weak bosons and cosmic antimatter
A program for using high energy neutrino astronomy with large neutrino detectors to directly test for the existence of heavier weak intermediate vector bosons (ivb) and cosmic antimatter is described. Such observations can provide a direct test of baryon symmetric cosmologies. Changes in the total cross section for nu(N) yields mu(X) due to additional propagators are discussed and higher mass resonances in the annihilation channel bar-nu sub e e(-) yields X are analyzed. The annihilation channel is instrumental in the search for antimatter, partcularly if heavier IVB's exist.
Brown, R. W.↗
DUMAND Summer Workshop, University of California, La Jolla, Calif., July 24-September 2, 1978, Proceedings. Volume 2 - UHE interactions, neutrino astronomy
The volume covers categories on inelastic neutrino scattering and the W-boson, and other ultra-high-energy processes, on pulsars, quasars and galactic nuclei, as well as other point sources and constants from gamma ray astronomy. Individual subjects include weak intermediate vector bosons and DUMAND, the Monte Carlo simulation of inelastic neutrino scattering in DUMAND, and Higgs boson production by very high-energy neutrinos. The observability of the neutrino flux from the inner region of the galactic disk, the diffuse fluxes of high-energy neutrinos, as well as the significance of gamma ray observations for neutrino astronomy are also among the topics covered.
Roberts, A.↗
NNPDF2.1: Including heavy quark mass effects in NNPDF fits
In this contribution we present the NNPDF2.1 parton distribution functions (PDF) set. The NNPDF2.1 set is a set extracted from a global fit to Deep-Inelastic Scattering (DIS), fixed target Drell-Yan (DY), Electroweak vector boson and inclusive jet cross-sections at colliders data. It is performed using the NNPDF methodology which relies on Monte Carlo techniques for determination of uncertainties and Neural Networks as unbiased interpolants.
72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
Search for a Vectorlike Quark with Charge 2/3 in t+Z Events from pp Collisions at {radical}(s)=7 TeV
A search for pair-produced heavy vectorlike charge-2/3 quarks, T, in pp collisions at a center-of-mass energy of 7 TeV, is performed with the CMS detector at the LHC. Events consistent with the flavor-changing-neutral-current decay of a T quark to a top quark and a Z boson are selected by requiring two leptons from the Z-boson decay, as well as an additional isolated charged lepton. In a data sample corresponding to an integrated luminosity of 1.14 fb{sup -1}, the number of observed events is found to be consistent with the standard model background prediction. Assuming a branching fraction of 100% for the decay T{yields}tZ, a T quark with a mass less than 475 GeV/c{sup 2} is excluded at the 95% confidence level.
72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
Neutrino Phenomenology of gauged L{sub {mu}}--L{sub {tau}}: MINOS and beyond
If a Z'gauge boson from a gauged L{sub {mu}}--L{sub {tau}} symmetry is very light, it is associated with a long-range leptonic force. In this case the particles in the Sun create via mixing of the Z'with the Standard Model Z a flavor-dependent potential for muon neutrinos in terrestrial long-baseline experiments. The potential changes sign for anti-neutrinos and hence can lead to apparent differences in neutrino and anti-neutrino oscillations without introducing CP or CPT violation. This could for instance explain the recently found discrepancy in the MINOS experiment. We obtain the associated parameters of gauged L{sub {mu}}--L{sub {tau}} required to explain this anomaly. The consequences for future long-baseline experiments are also discussed, and we compare the scenario to standard NSIs. When used to explain MINOS, both approaches have severe difficulties with existing limits.
72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
Highlights from RHIC Spin Physics Program
The Relativistic Heavy Ion Collider (RHIC) at Brookhaven National Laboratory delivers the world's highest energy polarized proton-proton collisions at a center of mass energy up to 500 GeV and provides a unique opportunity to study the quark and gluon spin structure of the proton and QCD dynamics at high energy scale. RHIC has produced many exiting physics results in recent years. The latest data from RHIC significantly constrain the gluon spin contribution to the proton spin, and the parity violating single spin asymmetry are observed for the first time in W production by both the PHENIX and STAR collaborations. In this report, I present the latest results from the PHENIX and STAR experiments, followed by a brief discussion of the future prospects of transverse physics, particularly on the importance of the unique measurements of Drell-Yan single spin asymmetry.
72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
{gamma}Z exchange corrections in parity-violating electron scattering
I report on recent work on two-boson exchange contributions ({gamma}{gamma} and {gamma}Z) and their implications for parity-violating electron scattering measurements. These calculations are particularly relevant for high precision measurements of the strange electric and magnetic form factors, and the weak charge of the proton.
72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
Wilson Prize article: Reflections on our experiences with developing the theory of intrabeam scattering
We discuss our experiences with developing detailed theoretical descriptions of intrabeam scattering in particle accelerators. We focus on the historical importance of understanding intrabeam scattering for the successful operation of a variety of accelerators around the world. In doing so, we highlight the fact that the theoretical understanding of intrabeam scattering played a crucial role in the discovery of the top quark at Fermilab, intermediate vector bosons W ± , Z and the Higgs particle at CERN, and the perfect liquid quark-gluon plasma at Brookhaven’s Relativistic Heavy Ion Collider. We describe several useful high energy approximations to intrabeam scattering, including those that utilize a Modified Piwinski high energy approximation by Karl Bane that has gained wide usage in applications to electron damping rings and advanced light sources. Finally, we comment on the fact that a detailed understanding of intrabeam scattering at synchrotron-based advanced light sources is empowering many transformational discoveries in a myriad of disciplines.
43 PARTICLE ACCELERATORS↗
Measurement of the top quark Yukawa coupling from t t ¯ kinematic distributions in the lepton + jets final state in proton-proton collisions at s = 13 TeV
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72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
Measurement of the top-quark mass in the lepton+jets channel using a matrix element technique with the CDF II detector
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72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
Search for resonant production of t t ¯ decaying to jets in p p ¯ collisions at s = 1.96 TeV
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Aaltonen, T.↗
Top quark forward-backward asymmetry, flavor-changing neutral-current decays, and like-sign pair production as a joint probe of new physics
The anomaly of the top quark forward-backward asymmetry A{sub FB}{sup t} observed at the Tevatron can be explained by the t-channel exchange of a neutral gauge boson (Z{sup '}) which has sizable flavor-changing coupling for top and up quarks. This gauge boson can also induce the top quark flavor-changing neutral-current (FCNC) decays and the like-sign top pair production at the LHC. In this work, we focus on two models which predict such a Z', namely, the left-right model and the U(1){sub X} model, to investigate the correlated effects on A{sub FB}{sup t}, the FCNC decays t{yields}uV (V=g, Z, {gamma}) and the like-sign top pair production at the LHC. We also pay special attention to the most recently measured A{sub FB}{sup t} in the large top pair invariant mass region. We find that under the current experimental constraints both models can alleviate the deviation of A{sub FB}{sup t} and, meanwhile, enhance the like-sign top pair production to the detectable level of the LHC. We also find that the two models give different predictions for the observables and their correlations, and thus they may even be distinguished by jointly studying these top quark observables.
72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
Finding physics signals with shower deconstruction
We introduce shower deconstruction, a method to look for new physics in a hadronic environment. The method aims to be a full information approach using small jets. It assigns to each event a number {chi} that is an estimate of the ratio of the probability for a signal process to produce that event to the probability for a background process to produce that event. The analytic functions we derive to calculate these probabilities mimic what full event generators like Pythia or Herwig do and can be depicted in a diagrammatic way. As an example, we apply this method to a boosted Higgs boson produced in association with a Z boson and show that this method can be useful to discriminate this signal from the Z+jets background.
72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
Z{gamma}{gamma} production with leptonic decays and triple photon production at next-to-leading order QCD
We present a calculation of the O({alpha}{sub s}) QCD corrections to the production of a Z boson in association with two photons and to triple-photon production at hadron colliders. All final-state photons are taken as real. For the Z boson, we consider the decays both into charged leptons and into neutrinos including all off-shell effects. Numerical results are obtained via a Monte Carlo program based on the structure of the VBFNLO program package. This allows us to implement general cuts and distributions of the final-state particles. We find that the next-to-leading order QCD corrections are sizable and significantly exceed the expectations from a scale variation of the leading-order result. In addition, differential distributions of important observables change considerably. The prediction of two-photon-associated Z production with Z decays into neutrinos from the charged-lepton rate works well, once we use an additional cut on the invariant mass of the charged-lepton pair.
72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
Gauged L{sub {mu}}-L{sub {tau}} symmetry at the electroweak scale
The extension of the standard model by a spontaneously broken abelian gauge group based on the L{sub {mu}}-L{sub {tau}} lepton number can resolve the long-standing discrepancy between experimental and theoretical values for the magnetic moment of the muon. It furthermore naturally generates {mu}-{tau} symmetric lepton mixing, introduces neutrino nonstandard interactions, and the associated gauge boson Z' serves as a mediator to the right-handed neutrino sector. A detailed fit to electroweak data is performed to identify the allowed values for the mass of Z' and its mixing with the standard model Z. An economical new scalar sector is constructed that spontaneously breaks L{sub {mu}}-L{sub {tau}} and leads to experimental consequences such as lepton flavor violation and collider signatures. Furthermore we discuss the nonabelian extension to an SU(2){sup '}, particularly the neutrino sector.
72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗