arXiv subjects

V. Barger

Publications and source records attributed to V. Barger.

At least 127 records · Page 7Linked to original sources

arXiv1998

Supersymmetry vis-a-vis Muon Colliders

The potential of muon colliders to study a low-energy supersymmetry is addressed in the framework of the minimal supergravity model, whose predictions are first briefly surveyed. Foremost among the unique features of a muon collider is s-channel production of Higgs bosons, by which Higgs boson masses, widths, and couplings can be precisely measured to test the predictions of supersymmetry. Measurements of the threshold region cross sections of W^+ W^-, t t-bar, Zh, chargino pairs, slepton and sneutrino pairs will precisely determine the corresponding masses and test supersymmetric radiative corrections. At the high-energy frontier a 3 to 4 TeV muon collider is ideally suited to study heavy scalar supersymmetric particles.

hep-ph↗

arXiv1998

Supersymmetry Phenomenology at Hadron Colliders

The phenomenology of a low-energy supersymmetry at hadron colliders is discussed with consideration of the minimal supergravity model, with a large top quark Yukawa coupling at the grand unification mass scale, and gauge mediated symmetry breaking models. Possible supersymmetry interpretations of some unexplained events are mentioned.

hep-ph↗

arXiv1998

Supersymmetry Phenomenology

The phenomenological implications of a low-energy supersymmetry are surveyed, with particular attention given to unification constraints and the role of a large top quark Yukawa couplings. Generic expectations for sparticle mass spectra are presented along with prospects for their discovery and study at present and future colliders.

hep-ph↗

arXiv1998

Physics at Muon Colliders

The potential of muon colliders to address fundamental physics issues is explored, with emphasis on understanding the nature of electroweak symmetry breaking. The $s$-channel production of Higgs bosons, unique to a muon collider, along with precision measurements of W^+W^-, t\bar t, and Zh thresholds would determine the properties of Higgs bosons and test electroweak radiative corrections. At the high energy frontier, a 4 TeV muon collider is ideally suited to study either the production of supersymmetric scalar particles or a strongly interacting WW sector.

hep-ph↗

arXiv1998

Chargino mass determination at a muon collider

We analyze the prospects at a muon collider for measuring chargino masses in the $μ^+μ^-\to \tildeχ^+\tildeχ^-$ process in the threshold region. We find that for the lighter chargino of a mass $100-200$ GeV, a measurement better than $50-300$ MeV should be possible with 50 fb$^{-1}$ integrated luminosity. The accuracy obtained here is better than with other techniques or at other facilities. The muon sneutrino mass, which enters through the $\tildeν_μ$ exchange diagram, can also be simultaneously measured to a few GeV if it is not too heavy.

hep-ph↗

arXiv1997

Four-Way Neutrino Oscillations

We present a four-neutrino model with three active neutrinos and one sterile neutrino which naturally has maximal $ν_μ\toν_τ$ oscillations of atmospheric neutrinos and can explain the solar neutrino and LSND results. The model predicts $ν_e \to ν_τ$ and $ν_e \to ν_μ$ oscillations in long-baseline experiments with $L/E \gg 1$ km/GeV with amplitudes that are determined by the LSND oscillation amplitude and argument controlled by the atmospheric $δm^2$.

hep-ph↗

arXiv1997

Relic Density of Neutralino Dark Matter in Supergravity Models

We calculate the relic density ($Ω_{χ^0_1} h^2$) of neutralino dark matter in supergravity models with radiative electroweak symmetry breaking, for values of the Higgs sector parameter $\tanβ\equiv v_2/v_1$ between the two infrared fixed points of the top quark Yukawa coupling, $\tanβ\simeq 1.8$ and $\tanβ\simeq 56$. For $\tanβ\alt 10$, the CP-odd Higgs pseudoscalar ($A^0$) and the heavier CP-even Higgs scalar ($H^0$) are much heavier than the lightest neutralino ($χ^0_1$), and the annihilation cross section of $χ^0_1$ pairs is significantly enhanced only in the vicinity of the lighter CP-even Higgs boson ($h^0$) and the $Z$ boson poles. For $\tanβ\agt 40$, $m_A$ and $m_H$ become comparable to $2m_{χ^0_1}$, and the neutralino annihilation cross section can be significantly enhanced by the poles of the $H^0$ and the $A^0$ as well. For a cosmologically interesting relic density, $0.1 \alt Ω_{χ^0_1} h^2 \alt 0.5$, we find that the supergravity parameter space is tightly constrained. The mass spectra for supersymmetric particles are presented for unification mass parameters in the cosmologically interesting region.

hep-ph↗

arXiv1997

Detecting the Higgs Bosons of Minimal Supergravity with Muon Pairs

The prospects at the CERN LHC are investigated for the discovery via decays into muon pairs of neutral Higgs bosons in the minimal supergravity model. Promising results are found for the CP-odd pseudoscalar ($A^0$) and the heavier CP-even scalar ($H^0$) Higgs bosons at large $\tanβ\equiv v_2/v_1$. For $\tanβ\agt 10$ and 100 GeV $\alt m_A,m_H \alt$ 550 GeV, the $A^0$ and the $H^0$ masses could be precisely reconstructed from the dimuon invariant mass.

hep-ph↗

arXiv1997

Relaxing Atomic Parity Violation Constraints on New Physics

The weak charge $Q_W$ measured in atomic parity violation experiments can receive compensating contributions from more than one new physics source. We show explicitly that the $ΔQ_W$ contribution from the exchange of an extra Z-boson can cancel that from the $s$-channel scalar top or scalar charm exchange in R-parity violating SUSY models proposed to explain the HERA high-$Q^2$ anomaly.

hep-ph↗

arXiv1997

Sparticle Production in Electron-Photon Collisions

We explore the potential of electron-photon colliders to measure fundamental supersymmetry parameters via the processes $eγ\to \tilde e \tildeχ^0$ (selectron-neutralino) and $eγ\to \tildeν\tildeχ^-$ (sneutrino-chargino). Given the $\tildeχ^0$ and $\tildeχ^-$ masses from $e^+e^-$ and hadron collider studies, cross section ratios $σ(γ_-)/σ(γ_+)$ for opposite photon helicities determine the $\tildeν_L$, $\tilde e_L$ and $\tilde e_R$ masses, independent of the sparticle branching fractions. The difference $m_{\tildeν_L}^2-m_{\tilde e_L}^2$ measures $M_W^2\cos2β$ in a model-independent way. The $\tilde e_L$ and $\tilde e_R$ masses test the universality of soft supersymmetry breaking scalar masses. The cross section normalizations provide information about the gaugino mixing parameters.

hep-ph↗

arXiv1997

Global Study of Electron-Quark Contact Interactions

We perform a global fit of data relevant to $eeqq$ contact interactions, including deep inelastic scattering at high $Q^2$ from ZEUS and H1, atomic physics parity violation in Cesium from JILA, polarized $e^-$ on nuclei scattering experiments at SLAC, Mainz and Bates, Drell-Yan production at the Tevatron, the total hadronic cross section $σ_{had}$ at LEP, and neutrino-nucleon scattering from CCFR. With only the new HERA data, the presence of contact interactions improves the fit compared to the Standard Model. When other data sets are included, the size of the contact contributions is reduced and the overall fit represents no real improvement over the Standard Model.

hep-ph↗

arXiv1997

Are $eμ$ colliders interesting?

We show that current experimental constraints already severely restrict what might be observable at $eμ$ colliders. We identify some cases where it may be possible to probe physics beyond what might be possible at other facilities and make some remarks about physics capability of high energy $eμ$ colliders.

hep-ph↗

arXiv1997

Higgs Searches at Future Colliders: Potentials for Discovery and Diagnosis

The prospects for Higgs boson discovery and study at present and future colliders are reviewed, with emphasis on the Minimal Supersymmetric Standard Model (MSSM) states. The expected experimental coverages with different production and decay modes are outlined. Particular attention is given to the Higgs couplings predicted when the top quark Yukawa coupling has an infrared fixed point. Characteristic Higgs boson mass spectra from the minimal supergravity (mSUGRA) model are considered and the decoupling/non-decoupling regimes of the lightest Higgs boson are discussed. General tests are described to ascertain whether a discovered light Higgs boson is a SM or MSSM state and to diagnose its fundamental properties. The constraints on the Higgs mass spectra implied by an interesting cosmological relic density of the lightest supersymmetric particle are described.

hep-ph↗

arXiv1997

The Physics Capabilities of mu^+ mu^- Colliders

We summarize the potential of muon colliders to probe fundamental physics. $W^+W^-$, \bar tt, and $Zh$ threshold measurements could determine masses to precisions $ΔM_W = 6$ MeV, $Δm_t = 70$ MeV, and $Δm_h = 45$ MeV, to test electroweak radiative corrections. With $s$-channel Higgs production, unique to a muon collider, the Higgs mass could be pinpointed ($Δm_h < 1$ MeV) and its width measured. The other Higgs bosons of supersymmetry can be produced and studied by three methods. If instead the $WW$ sector turns out to be strongly interacting, a 4 TeV muon collider is ideally suited to its study.

hep-ph↗

arXiv1997

Contact Interactions and high-Q2 events in e^+ p collisions at HERA

We consider $e e q q$ contact interactions as a possible origin of an excess of events above Standard Model predictions in $e^+ p \to e^+ jet$ at high $Q^2$ observed by the H1 and ZEUS collaborations at HERA. The HERA data prefer chirality RL or LR contact terms and atomic physics parity violation measurements severely limit parity-odd contact terms. With equal left-right and right-left chirality interactions at an effective scale of order 3 TeV we are able to reproduce the main features of the HERA data and still be consistent with Drell-Yan pair production at the Tevatron and hadron production at LEP 2 and TRISTAN.

hep-ph↗

arXiv1997

Precision W-boson and top-quark mass determinations at a muon collider

Precise determinations of the masses of the $W$ boson and of the top quark could stringently test the radiative structure of the Standard Model (SM) or provide evidence for new physics. We analyze the excellent prospects at a muon collider for measuring $M_W$ and $m_t$ in the $W^+W^-$ and $t\bar t$ threshold regions. With an integrated luminosity of 10 (100) fb$^{-1}$, the $W$-boson mass could be measured to a precision of 20 (6) MeV, and the top-quark mass to a precision of 200 (70) MeV, provided that theoretical and experimental systematics are understood. A measurement of $Δm_t=200$ MeV for fixed $M_W$ would constrain a 100 GeV SM Higgs mass within about $\pm 2$ GeV, while $ΔM_W=6$ MeV for fixed $m_t$ would constrain $m_h$ to about $\pm 10$ GeV.

hep-ph↗

arXiv1996

Precision Higgs boson mass determination at lepton colliders

We demonstrate that a measurement of the Bjorken process $e^+e^-, μ^+μ^-\to ZH$ in the threshold region can yield a precise determination of the Higgs boson mass. With an integrated luminosity of $100 fb^{-1}$, it is possible to measure the Higgs mass to within 60 MeV (100 MeV) for m_H=100 GeV (150 GeV).

hep-ph↗

arXiv1996

Studying a Strongly Interacting Electroweak Sector via Longitudinal Gauge Boson Scattering at a Muon Collider

We discuss the excellent prospects for a detailed study of a strongly interacting electroweak sector at a muon collider with c.m. energy $\rts\sim 4\tev$. For expected luminosity of $L=200-1000\fbi$ per year, $\mup\mum$ and $\mup\mup$ (or $\mum\mum$) collisions can be used to study longitudinal $\wp\wm$ and $\wp\wp$ (or $\wm\wm$) scattering with considerable precision. In particular, detailed measurements of the distribution in the $VV$ pair masses ($V=\wpm,Z$) will be possible. The shape and magnitude of these distributions will provide a powerful tool for determining the nature of strong gauge boson interactions. Event rates will be large enough that projection techniques can be used to directly isolate final states with different polarizations of the $V$'s and verify that the strong interaction cross section excess is mainly in the longitudinal-longitudinal mode.

hep-ph↗