arXiv subjects
Publications and source records attributed to Probir Roy.
The small difference between the survival probabilities of muon neutrino and antineutrino beams, traveling through earth matter in a long baseline experiment such as MINOS, is shown to be an important measure of any possible deviation from maximality in the flavor mixing of those states.
The perturbative treatment of subdominant oscillation and the matter effect in neutrino beams/superbeams, propagating over long baselines and being used to look for CP violation, is studied here for a general matter density function varying with distance. New lowest order analytic expressions are given for different flavour transition and survival probabilities in a general neutrino mixing basis and a variable earth matter density profile. It is demonstrated that the matter effect in the muon neutrino (antineutrino) flavour survival probability vanishes to this order, provided the depletion, observed for atmospheric muon neutrinos and antineutrinos at super-Kamiokande, is strictly maximal. This result is independent of the earth density profile and the distance L between the source and the detector. In the general variable density case we show that one cannot separate the matter induced asymmetry from a genuine CP effect by keeping two detectors at distances $L_1$ and $L_2$ from the source while maintaining a fixed ratio $L_1/E_1 = L_2/E_2$. This needs to be done numerically and we estimate the asymmetry generated by the earth matter effect with particular density profiles and some chosen parameters for very long baseline neutrino oscillation experiments.
Preliminary Remarks. Gauge mediated supersymmetry breaking. Gravity mediated supersymmetry breaking. Anomaly mediated supersymmetry breaking. Gaugino mediated supersymmetry breaking. Braneworld supersymmetry breaking. Conclusions.
All existing data on neutrino oscillations (including those from the LSND experiment) imply a four neutrino scheme with six different allowed mass patterns. Some of the latter are shown to be disfavored by using a conservative upper bound on the $βbeta 0 ν$ nuclear decay rate, if neutrinos are assumed to be Majorana particles. Comparisons are also made with restrictions from tritium $β$-decay and cosmology.
The three neutrino Zee model and its extension including three active and one sterile species are studied in the light of new neutrino oscillation data. We obtain analytical relations for the mixing angle in solar oscillations in terms of neutrino mass squared differences. For the four neutrino case, we obtain the result $\mathsf{sin^2 2 θ_\odot \approx 1 - [ (Δm^2_{Atm})^2/(4 Δm^2_{LSND} Δm^2_\odot) ]^2}$, which can accommodate both the large and small mixing scenarios. We show that within this framework, while both the SMA-MSW and the LMA-MSW solutions can easily be accommodated, it would be difficult to reconcile the LOW-QVO solutions. We also comment on the active-sterile admixture within phenomenologically viable textures.
Though the minimal model of anomaly mediated supersymmetry breaking has been significantly constrained by recent experimental and theoretical work, there are still allowed regions of the parameter space for moderate to large values of $\tanβ$. We show that these regions will be comprehensively probed in a ${\sqrt s} =1$ TeV $e^+e^-$ linear collider. Diagnostic signals to this end are studied by zeroing in on a unique and distinct feature of a large class of models in this genre: a neutral winolike Lightest Supersymmetric Particle closely degenerate in mass with a winolike chargino. The pair production processes $e^+e^- \to {\tilde e}_L^\pm {\tilde e}_L^\mp$, ${\tilde e}_R^\pm {\tilde e}_R^\mp$, ${\tilde e}_L^\pm {\tilde e}_R^\mp$, ${\tilde ν} {\bar {\tilde ν}}$, $\widetilde χ^0_1 \widetilde χ^0_2$, $\widetilde χ^0_2 \widetilde χ^0_2$ are all considered at $\sqrt s = 1$ TeV corresponding to the proposed TESLA linear collider in two natural categories of mass ordering in the sparticle spectra. The signals analysed comprise multiple combinations of fast charged leptons (any of which can act as the trigger) plus displaced vertices $X_D$ (any of which can be identified by a heavy ionizing track terminating in the detector) and/or associated soft pions with characteristic momentum distributions.
Selectron (smuon) pair-production in a next generation Linear Collider, yielding a fast electron (muon) trigger, a visible heavily ionizing track and/or a resolved soft pion impact parameter and overall $\mET$, is shown to provide a smoking gun signature for Anomaly Mediated Supersymmetry Breaking models with a neutral Wino as the Lightest Supersymmetric Particle, nearly mass-degenerate with the lighter chargino.
An unambiguous identification of glueballs in experiments will be of great significance, because their existence is an important test of QCD. The proposal, advanced here, is to experimentally search for glueballs as peaks in the invariant mass of a leading K_S-pair fragmenting from an energetic gluon jet out of high-statistics three-jet events in hadronic decays of the weak neutral Z boson. Using a physically motivated model of the gluon-glueball fragmentation function, we find a substantial fragmentation rate into a leading glueball. It is very likely that a search, along the lines suggested here by any of the four groups at the Large Electron Positron collider at CERN, will prove fruitful.
The radiative model, proposed by Zee, is extended from the three neutrino $(ν_{e,μ,τ})$ sector to include a fourth sterile neutrino $ν_s$. The oscillations $ν_e \leftrightarrow ν_s$ (solar), $ν_μ\leftrightarrow ν_τ$ (atmospheric) and $ν_e \leftrightarrow ν_μ$ (LSND) are invoked to explain all oscillation data with the successful relation $(Δm^2)_{atm} \simeq 2[(Δm^2)_{solar} (Δm^2)_{LSND}]^{1/2}$ as an added bonus.
Limits are derived on models with extended Higgs sectors, including the Minimal Supersymmetric Standard Model (MSSM), by exploiting the data on $τ^+ τ^- + $ 2 jets final states, used by the CDF collaboration to place limits on third generation leptoquarks. The main observation here is that both leptoquark production and associated $b \bar{b}$ Higgs production can lead to $b \bar{b} τ^+ τ^-$ final states.
A simple unifying mass matrix is presented for the three active and one sterile neutrinos $ν_e$, $ν_μ$, $ν_τ$ and $ν_s$, using an extension of the radiative mechanism proposed some time ago by Zee. The total neutrino-oscillation data are explained by the scheme $ν_e \leftrightarrow ν_s$ (solar), $ν_μ\leftrightarrow ν_τ$ (atmospheric) and $ν_e \leftrightarrow ν_μ$ (LSND). We obtain the interesting approximate relationship $(Δm^2)_{atm} \simeq 2[(Δm^2)_{solar} (Δm^2)_{LSND}]^{1/2}$ which is well satisfied by the data.
If one assumes solar and LSND neutrino oscillations to explain the corresponding data, then the atmospheric neutrino deficit cannot be accommodated within the Standard Model with three light flavors, unless one ignores the data's zenith-angle dependence. We propose a novel solution to this problem by postulating large anomalous diagonal $ν_τ$-quark interactions which affect $ν_μ- ν_τ$ oscillations traversing the Earth and induce the observed zenith-angle dependence.
$R_p$ and motivation for explicit $R\!\!\!/}_p$, MSSM $\rightarrow$ $ R\!\!\!/}_p$ MSSM, Bounds on ${R\!\!\!/}_p$ couplings, Collider-specific phenomenology, Cosmological implications, Summary and outlook, References
A reexamination is made of one-loop oblique electroweak corrections. General definitions are given of the oblique parameters without reference to any $q^2$-expansion scheme. The old oblique parameters S,T and U are defined as differences of gauge boson vacuum polarization $Π$-functions and suffice to describe certain observable ratios on the Z-peak and the $ρ$ parameter at $q^2=0$. Regarding the new oblique parameters V,W and X, the first two are defined in terms of differences of $Π$-functions as well as the wavefunction renormalization of the corresponding weak boson, and the third in terms of the difference of differences of two $Π$-functions for $γ-Z$ mixing. Explicit expressions for measurable quantities involving all six oblique parameters are given and experimental bounds are obtained on the latter, some for the first time. A review of these constraints suggests that the linear approximation of Peskin and Takeuchi is robust.
This paper is withdrawn. A revised and expanded version of this work is available as hep-ph/9603323.
1. Scope and motivation 2. Lightning review of CMSSM 3. LEP 1 bounds and LEP 1.5 results 4. LEP 2 futurology 5. Bottomline
This report summarises the work done during the Workshop on High Energy Physics Phenomenology 4 (S.N.Bose National Centre for Basic Sciences, Calcutta, India, Jan 2-14,1996) in Working Groups IV (Unification and Model Building) and V (Astroparticle Physics and Neutrinos).
Strong upper bounds are derived on certain product combinations of lepton nonconserving couplings in the minimal supersymmetric standard model with explicit $R$-parity violation. The input is information from rare leptonic decays of the long-lived neutral kaon, the muon and the tau as well as from the mixings of neutral $K$- and $B$-mesons. One of these bounds is comparable and another superior to corresponding ones obtained recently from neutrinoless double beta decay.