arXiv subjects

Howard E. Haber

Publications and source records attributed to Howard E. Haber.

At least 91 records · Page 5Linked to original sources

arXiv1999

How Well Can We Predict the Mass of the Higgs Boson of the Minimal Supersymmetric Model?

The upper bound on the mass of the light CP-even Higgs boson of the minimal supersymmetric model (MSSM) depends on the supersymmetric particle spectrum via radiative loop effects. At present, complete one-loop results and partial two-loop results are known. Some simple analytic approximations have been obtained which are quite accurate over a large portion of the MSSM parameter space. Based on these results, I examine how accurately one can predict the upper bound on the mass of the lightest MSSM Higgs boson.

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arXiv1998

(S)neutrino properties in R-parity violating supersymmetry: I. CP-conserving Phenomena

R-parity-violating supersymmetry (with a conserved baryon number B) provides a framework for particle physics with lepton number (L) violating interactions. We examine in detail the structure of the most general R-parity-violating (B-conserving) model of low-energy supersymmetry. We analyze the mixing of Higgs bosons with sleptons and the mixing of charginos and neutralinos with charged leptons and neutrinos, respectively. Implications for neutrino and sneutrino masses and mixing and CP-conserving sneutrino phenomena are considered. L-violating low-energy supersymmetry can be probed at future colliders by studying the phenomenology of sneutrinos. Sneutrino-antisneutrino mass splittings and lifetime differences can provide new opportunities to probe lepton number violation at colliders.

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arXiv1998

Low-Energy Supersymmetry at Future Colliders

We classify the variety of low-energy supersymmetric signatures that can be probed at future colliders. We focus on phenomena associated with the minimal supersymmetric extension of the Standard Model. The structure of the supersymmetry-breaking introduces additional model assumptions. The approaches considered here are supergravity-mediated and gauge-mediated supersymmetry-breaking. Alternative phenomenologies arising in non-minimal and/or R-parity-violating approaches are also briefly examined.

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arXiv1998

Probing the MSSM Higgs Sector at an e-e- Collider

The theoretical structure of the Higgs sector of the Minimal Supersymmetric Standard Model (MSSM) is briefly described. An outline of Higgs phenomenology at future lepton colliders is presented, and some opportunities for probing the physics of the MSSM Higgs sector at an e-e- collider are considered.

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arXiv1997

The Status of the Minimal Supersymmetric Standard Model and Beyond

The minimal supersymmetric extension of the Standard Model (MSSM) is reviewed. In the most general framework with minimal field content and R-parity conservation, the MSSM is a 124-parameter model (henceforth called MSSM-124). An acceptable phenomenology occurs only at exceptional points (and small perturbations around these points) of MSSM-124 parameter space. Among the topics addressed in this review are: gauge coupling unification, precision electroweak data, phenomenology of the MSSM Higgs sector, and supersymmetry searches at present and future colliders. The implications of approaches beyond the MSSM are briefly addressed.

hep-ph↗

arXiv1997

Higgs Boson Masses and Couplings in the Minimal Supersymmetric Model

The Higgs sector of the Minimal Supersymmetric Model (MSSM) is a CP-conserving two-Higgs doublet model that depends, at tree-level, on two Higgs sector parameters. In order to accurately determine the phenomenological implications of this model, one must include the effects of radiative corrections. The leading contributions to the one-loop radiative corrections are exhibited; large logarithms are resummed by the renormalization group method. Implications for Higgs phenomenology are briefly discussed.

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arXiv1997

Weakly-Coupled Higgs Bosons and Precision Electroweak Physics

We examine the prospects for discovering and elucidating the weakly-coupled Higgs sector at future collider experiments. The Higgs search consists of three phases: (i) discovery of a Higgs candidate, (ii) verification of the Higgs interpretation of the signal, and (iii) precision measurements of Higgs sector properties. The discovery of one Higgs boson with Standard Model properties is not sufficient to expose the underlying structure of the electroweak symmetry breaking dynamics. It is critical to search for evidence for a non-minimal Higgs sector and/or new physics associated with electroweak symmetry breaking dynamics. An improvement in precision electroweak data at future colliders can play a useful role in confirming the theoretical interpretation of the Higgs search results.

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arXiv1997

Future Directions in Higgs Phenomenology

The search for the weakly-coupled Higgs sector at future colliders consists of three phases: discovery of a Higgs candidate, verification of the Higgs interpretation of the signal, and precision measurements of Higgs sector properties. The discovery of one Higgs boson with Standard Model properties is not sufficient to expose the underlying structure of the electroweak symmetry breaking dynamics. It is critical to search for evidence for a non-minimal Higgs sector and/or new physics associated with electroweak symmetry breaking dynamics.

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arXiv1997

Sneutrino Mixing Phenomena

In any model with nonzero Majorana neutrino masses, the sneutrino and antisneutrino of the supersymmetric extended theory mix. We outline the conditions under which sneutrino-antisneutrino mixing is experimentally observable. The mass-splitting of the sneutrino mass eigenstates and sneutrino oscillation phenomena are considered.

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arXiv1996

Approximating the radiatively corrected Higgs mass in the Minimal Supersymmetric Model

To obtain the most accurate predictions for the Higgs masses in the minimal supersymmetric model (MSSM), one should compute the full set of one-loop radiative corrections, resum the large logarithms to all orders, and add the dominant two-loop effects. A complete computation following this procedure yields a complex set of formulae which must be analyzed numerically. We discuss a very simple approximation scheme which includes the most important terms from each of the three components mentioned above. We estimate that the Higgs masses computed using our scheme lie within 2 GeV of their theoretically predicted values over a very large fraction of MSSM parameter space.

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arXiv1996

Recent Refinements in Higgs Physics

Recent refinements of the phenomenology of Higgs bosons in the Standard Model and the Minimal Supersymmetric Standard Model are reviewed.

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arXiv1996

Supersymmetric Hints from Precision Electroweak Data?

The Standard Model does not provide a very good fit to the most recent precision electroweak data from LEP, due primarily to the observed branching ratios for $Z$ decay to $b\bar b$ and $c\bar c$. The possibility that an extension of the Standard Model with low-energy supersymmetry can improve the agreement between data and theory is considered.

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arXiv1995

Low-Energy Supersymmetry: Prospects and Challenges

An introduction to the minimal supersymmetric Standard Model (MSSM) is given. The motivation for ``low-energy'' supersymmetry is reviewed, and the structure of the MSSM is outlined. In its most general form, the MSSM can be viewed as a low-energy effective theory parametrized by a set of arbitrary soft-supersymmetry-breaking parameters. A variety of techniques for reducing the parameter freedom of the MSSM are surveyed. The search for supersymmetry below and above the threshold for supersymmetric particle production presents a challenging task for experimentalists at present and future colliders.

hep-ph↗

arXiv1995

QCD corrections to charged Higgs-mediated $b \to c τν$ decay

We calculate the $O(α_s)$ corrections to the charged Higgs mediated inclusive semi-tauonic $B$ decay. By working in the Landau gauge, we demonstrate how to obtain the charged Higgs contributions (both direct and interference terms) from the known QCD corrections to $t \to b H^+$. Combining our results with $O(1/m_b^2)$ corrections to the spectator model and comparing the theoretical prediction with the recent experimental measurements, we find a model-independent $2σ$ upper bound on the ratio of Higgs vacuum expectation values, $\tanβ<0.52(m_H/1 GeV)$.

hep-ph↗

arXiv1995

Is $M_t\simeq M_w$ Ruled Out?

A four generation supersymmetric model is proposed, in which the Tevatron ``top-quark'' events are reinterpreted as the production of $t^\prime$ which decays dominantly to $bW^+$. In this model, $m_t\simeq m_W$, and $t\rta\widetilde t\widetildeχ^0_1$, with $\widetilde t\rta c\widetildeχ^0_1$. This decay chain, which rarely produces a hard isolated lepton, would have been missed in all previous top quark searches. A narrow region of the model parameter space exists which cannot yet be ruled out by present data. This model predicts a rich spectrum of new physics which can be probed at LEP-II and the Tevatron.

hep-ph↗

arXiv1995

Challenges For Non-Minimal Higgs Searches at Future Colliders

In models with a non-minimal Higgs sector, the lightest scalar state may be a neutral CP-even Higgs boson, whose properties are nearly identical to those of the minimal Higgs boson of the Standard Model. In such a scenario, the other Higgs scalars are significantly heavier than $m_Z$; their effects rapidly decouple from the low-energy theory. The decoupling limit of the most general CP-conserving two-Higgs doublet model is formulated. Detection of evidence for a non-minimal Higgs sector in the decoupling limit presents a formidable challenge for Higgs searches at future colliders.

hep-ph↗

arXiv1995

Non-Minimal Higgs Sectors: The Decoupling Limit and its Phenomenological Implications,

In models with a non-minimal Higgs sector, a decoupling limit can be defined. In this limit, the masses of all the physical Higgs states are large (compared to the scale of electroweak symmetry breaking) except for one neutral CP-even Higgs scalar, whose properties are indistinguishable from the Higgs boson of the minimal Standard Model. The decoupling limit of the most general CP-conserving two-Higgs doublet model is formulated. Detection of evidence for a non-minimal Higgs sector at future colliders in the decoupling limit may present a formidable challenge for future Higgs searches.

hep-ph↗

arXiv1994

Spin Formalism and Applications to New Physics Searches

An introduction to spin techniques in particle physics is given. Among the topics covered are: helicity formalism and its applications to the decay and scattering of spin-1/2 and spin-1 particles, techniques for evaluating helicity amplitudes (including projection operator methods and the spinor helicity method), and density matrix techniques. The utility of polarization and spin correlations for untangling new physics beyond the Standard Model at future colliders such as the LHC and a high energy $e^+e^-$ linear collider is then considered. A number of detailed examples are explored including the search for low-energy supersymmetry, a non-minimal Higgs boson sector, and new gauge bosons beyond the $W^\pm$ and $Z$.

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