arXiv subjects
Publications and source records attributed to J. Kalinowski.
Formation of the $s$-channel slepton resonances at LEP2 or Tevatron at current energies is an exciting possibility in R-parity violating SUSY models. Existing LEP2 and Tevatron data can be exploited to look for sleptons, or to derive bounds on the Yukawa couplings of sleptons to quark and lepton pairs.
Charginos $χ_1^\pm$ are expected to be the lightest observable supersymmetric particles in many supersymmetric models. We present a procedure which will allow to determine the chargino mixing angles and, subsequently, the fundamental SUSY parameters $M_2, μ$ and $\tanβ$ by measurements of the total cross section and the spin correlations in $e^+e^-$ annihilation to $χ_1^+ χ_1^-$ chargino pairs.
The process e+e- to nu barnu + gamma with a distinctive ``photon-plus-missing-energy'' signal can serve as an important tool to search for new physics at LEP2. It can be exploited to measure the WW gamma coupling, or to search for weakly interacting and invisible (s)particles. For meaningful comparisons of experimental data with theoretical predictions, higher-order QED corrections due to multiphoton emission must be taken into account. In the present paper we explain how the WW gamma coupling has been incorporated into the KORALZ Monte Carlo program, which can now be used for simulations of e+e- to nu bar nu + gamma events with higher-order QED corrections. The strategy of how to perform an experimental analysis in the presence of experimental cuts is proposed. The question of systematic uncertainties is addressed and some numerical results for the phenomenologically interesting case of anomalous WW gamma couplings are also given.
In supersymmetric theories with R-parity breaking, sleptons can be produced in quark-antiquark annihilation at the Tevatron through interactions in which two quark fields are coupled to a slepton field. If at the same time trilinear slepton-lepton-lepton couplings are present, the sleptons can be searched for as resonances in $p\bar{p}\to \tildeν \to l^+l^-$ and $\tildeτ\to lν$ final states. Existing Tevatron data can be exploited to derive bounds on the Yukawa couplings of sleptons to quark and lepton pairs. Similar bounds can also be obtained from $e^+e^-$ annihilation to hadrons at LEP2.
The impact of virtual leptoquark or R-parity breaking squark exchange as well as generic contact interactions on the production of quark-antiquark pairs in $e^+e^-$ annihilation, in particular at LEP2, is summarized. An exciting possibility of sneutrino formation in $e^+e^-$ scattering is also mentioned.
We describe the Fortran code HDECAY which calculates the decay widths and the branching ratios of the Standard Model Higgs boson, and of the neutral and charged Higgs particles of the Minimal Supersymmetric extension of the Standard Model. The program is self-contained (with all subroutines included), easy to run, fast and calculates the decay widths and branching ratios according to the current theoretical knowledge.
We derive a sum rule which shows how to extend LEP limits on the masses of the lightest CP-even and CP-odd Higgs bosons of a CP-conserving two-Higgs-doublet model to any two Higgs bosons of a general CP-violating two-Higgs-doublet model. We generalize the analysis to a Higgs sector consisting of an arbitrary number of Higgs doublets and singlets, giving explicit limits for the CP-conserving and CP-violating two-doublet plus one-singlet Higgs sectors.
In supersymmetric theories with R-parity breaking, trilinear couplings of two leptons to scalar sleptons are possible. In electron-positron collisions such interactions would manifest themselves through contact terms in Bhabha scattering and in annihilation to mu or tau pair Interpreting the high x, high Q2 DIS HERA events as charm squark production with squark masses of order 200 GeV, the formation of tau sneutrinos with a mass in the range close to the LEP2 energy or even in reach, is an exciting speculation which can be investigated in the coming LEP2 runs with energies close to 200 GeV.
In reference to the recently observed high Q^2, large x events in deep-inelastic positron-proton scattering at HERA, various leptoquark and supersymmetric scenarios are discussed. We study the impact of virtual leptoquark or R-parity breaking squark exchange as well as generic contact interaction on the production of quark-antiquark pairs in $e^+e^-$ annihilation, in particular at LEP2.
The region of the supersymmetry parameter space, in which charginos decay predominantly into sneutrinos and leptons: chi+ -> \tildeν + l+, is not excluded experimentally for small mass differences between charginos and sneutrinos. The decay sneutrinos are invisible in R-parity conserving theories since they are either the lightest supersymmetric particles or they decay primarily into the channel: neutrino + lightest neutralino. If the energy of the decay leptons is so small that they escape detection, chargino events e+e- -> chi+chi- in e+e- collisions remain invisible, eroding the excluded chargino mass range at LEP. This region of the supersymmetry parameter space can partly be covered by searching for single W events in e+e- -> W+W-$, with one W boson decaying to leptons or quark jets, but the second W boson decaying to (undetected) charginos and neutralinos.
Estimates for longitudinal spin asymmetries which single out new polarized nucleon structure functions in deeply inelastic charged current interactions at HERA energies are given, exploiting their interpretation in terms of polarized quark distributions. These asymmetries turn out to be large and allow a measurement of the new polarized structure functions $g_1^{W}$ and $g_5^{W}$, which would add valuable tests and information on the spin content of quarks inside a polarized proton. We also show that single spin asymmetries in neutral current interactions are very small.
The production mechanisms and decay modes of the heavy neutral and charged Higgs bosons in the Minimal Supersymmetric Standard Model are investigated at future $e^+ e^-$ colliders in the TeV energy regime. We generate supersymmetric particle spectra by requiring the MSSM Higgs potential to produce correct radiative electroweak symmetry breaking, and we assume a common scalar mass $m_0$, gaugino mass $m_{1/2}$ and trilinear coupling $A$, as well as gauge and Yukawa coupling unification at the Grand Unification scale. Particular emphasis is put on the low $\tb$ solution in this scenario where decays of the Higgs bosons to Standard Model particles compete with decays to supersymmetric charginos/neutralinos as well as sfermions. In the high $\tb$ case, the supersymmetric spectrum is either too heavy or the supersymmetric decay modes are suppressed, since the Higgs bosons decay almost exclusively into $b$ and $τ$ pairs. The main production mechanisms for the heavy Higgs particles are the associated $AH$ production and $H^+H^-$ pair production with cross sections of the order of a few fb.
Among the possible decay modes of Higgs particles into supersymmetric states, neutralino and chargino decays play a prominent rôle. The experimental opportunities of observing such decay modes at LEP2 and at future e+e- linear colliders are analyzed within the frame of the Minimal Supersymmetric extension of the Standard Model. For heavy Higgs particles, the chargino/neutralino decay modes can be very important, while only a small window is open for the lightest CP-even Higgs particle. If charginos/neutralinos are found at LEP2, such decay modes can be searched for in a small area of the parameter space, and invisible decays may reduce the exclusion limits of the lightest CP-even Higgs particle slightly; if charginos/neutralinos are not found at LEP2 in direct searches, the Higgs search will not be affected by the SUSY particle sector.
In this report we review the prospects for Higgs physics at LEP2. The theoretical aspects and the phenomenology of Higgs particles are discussed within the Standard Model (SM) and the Minimal Supersymmetric Standard Model (MSSM). The experimental search techniques are described and the discovery limits for Higgs bosons in the LEP2 energy range are summarized. In addition, opportunities of detecting Higgs particles in non-minimal extensions of the SM and the MSSM are investigated.
We present the results obtained by the "Triple Gauge Couplings" working group during the LEP2 Workshop (1994-1995). The report concentrates on the measurement of $WWγ$ and $WWZ$ couplings in $e^-e^+\to W^-W^+$ or, more generally, four-fermion production at LEP2. In addition the detection of new interactions in the bosonic sector via other production channels is discussed.
We summarize the dominant decay modes of the neutral and charged Higgs bosons in the Minimal Supersymmetric extension of the Standard Model. While two--body decays are in general dominating, the branching ratios for three--body decays of the heavy scalar, pseudoscalar and charged Higgs bosons can be large below the thresholds if top quarks, $W/Z$ bosons or heavy scalar bosons are involved. Analytical expressions have been derived for the partial decay widths and the physical implications of these decay modes are discussed.
Large fermion mass effect on the Yukawa process $Z \ra b\bar{b}\ra b\bar{b} h (A)$ in the entire range of the neutral Higgs boson masses is found. It is particularly important for light Higgs bosons, which are still not excluded experimentally in a general two-Higgs-doublet model.
We investigate the sensitivity of single photon plus missing energy cross-sections at future $e^{+}e^{-}$ linacs to non-standard $WWγ$ couplings. We show that even with conservative estimates of systematic errors there is still considerable sensitivity to anomalous couplings. Analytic expressions for helicity amplitudes are presented.