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J. Wudka

Publications and source records attributed to J. Wudka.

At least 19 recordsLinked to original sources
arXiv2019

Ultra light Thomas-Fermi Dark Matter

We investigate the viability of a simple dark matter (DM) model consisting of a single fermion in the context of galactic dynamics. We use a consistent approach that does not presume a particular DM density profile but instead requires that the DM+baryon system is in hydrostatic equilibrium. Using a phenomenological baryon density profile, the model then predicts the DM distribution with a core like behavior close to the galactic center. The presence of supermassive black holes (SMBHs) in the center of large galaxies arises naturally in this framework. Using data from a set of large elliptical and spiral galaxies, and from a small set of dwarf galaxies, we find that the model can explain most of the bulk galactic properties, as well as some of the features observed in the rotation curves, provided the DM mass is in the $\mathcal{O}$(50 eV) range. More precise tests of the model require better modeling of the baryon profile and better control on the uncertainties in the data.

astro-ph.GA↗
arXiv2019

Strongly Interacting Neutrino Portal Dark Matter

We present a realistic, simple and natural model of strongly-interacting dark matter based on the neutrino-portal paradigm. The strong interactions at small velocities are generated by the exchange of dark photons, and produce the observed core-like DM distribution in galactic centers; this effect could be spoiled by the formation of DM bound states (also due to dark-photon effects), which we avoid by requiring the DM candidates to be light, with masses below O(10 GeV). The mixing of the dark photon with the Z and ordinary photon is strongly suppressed by introducing a softly-broken discrete symmetry similar to charge conjugation, which also ensures that the dark photon life-time is short enough to avoid restrictions derived form big-bang nucleosynthesis and large-scale structure formation. Other constraints are accommodated without the need of fine tuning, in particular nucleon scattering occurs only at one loop, so direct detection cross sections are naturally suppressed. Neutrino masses are generated through the inverse see saw.

hep-ph↗
arXiv2019

Asymmetric dark matter with a possible Bose-Einstein condensate

We investigate the properties of a Bose gas with a conserved charge as a dark matter candidate, taking into account the restrictions imposed by relic abundance, direct and indirect detection limits, big-bang nucleosynthesis and large scale structure formation constraints. We consider both the WIMP-like scenario of dark matter masses $ \gtrsim $ 1 GeV, and the small mass scenario, with masses $ \lesssim 10^{-11} $ eV. We determine that a Bose-Einstein condensate will be present at sufficiently early times, but only for the small-mass scenario it will remain at the present epoch.

hep-ph↗
arXiv2013

Neutrinoless double $β$ decay with small neutrino masses

If the only contribution to neutrinoless double beta decay (NLDBD) are neutrino masses its discovery may be very difficult, especially if neutrinos present a normal hierarchy spectrum. However, this is not the only possibility; NLDBD can in general produce electrons of either chirality, in contrast with the neutrino induced NLDBD which predicts two left-handed electrons. Using an effective Lagrangian approach we classify the lepton number violating (LNV) effective operators with two leptons of either chirality but no quarks, ordered according to the magnitude of their contribution to NLDBD. We point out that, for each of the three chirality assignments, $e_{L}e_{L},e_{L}e_{R}$ and $e_{R}e_{R}$, there is only one LNV operator of the corresponding type to lowest order, and these have dimensions 5, 7 and 9, respectively. Neutrino masses are always induced by these extra operators but can be delayed to one (dimension 7) or two loops (dimension 9). Under the assumption that NLDBD is dominated by the operators of dimension 7 or 9 we find that the scale of new physics should be relatively low ($\lesssim 30$ TeV). We also list the SM additions generating these operators upon integration of the heavy modes, and discuss simple realistic examples of renormalizable theories for each case. The phenomenology of a model giving rise to the dimension 9 operator has been analyzed with some detail: if NLDBD is going to be seen in the next round of experiments, the doubly charged scalars of the model could be seen at the LHC and lepton flavour violating (LFV) rates could be at the reach of foreseen experiments. Moreover neutrino masses, which arise at two loops, display a very particular structure and are strongly constrained, in fact, $\sin^{2}θ_{13}\gtrsim0.008$, when $μ\rightarrow eee$ is required to lie below its present experimental limit.

hep-ph↗
arXiv2009

Evidence for right-handed neutrinos at a neutrino factory

We emphasize that a muon based neutrino factory could show the existence of light right-handed neutrinos, if a deficit in the number of detected events is observed at a near detector. This could be as large as ~10% if the size of the new interactions saturates the present limits from electroweak precision data, what is not excluded by the oscillation experiments performed up to now. A simple model realizing such a scenario can be obtained adding right-handed neutrinos to the minimal Standard Model, together with an extra scalar doublet and a triplet of hypercharge 1. In this case, however, the possible deficit is reduced by a factor of ~3, and the Yukawa couplings must be adequately chosen. This is also generically required if lepton flavour violation must be below present bounds.

hep-ph↗
arXiv2002

Present and Future Electroweak Precision Measurements and the Indirect Determination of the Mass of the Higgs Boson

We discuss the experimental and theoretical uncertainties on precision electroweak observables and their relationship to the indirect constraints on the Higgs-boson mass, $\MH$, in the Standard Model (SM). The critical experimental measurements ($\MW$, $\sweff$, $\mt$, ...) are evaluated in terms of their present uncertainties and their prospects for improved precision at future colliders, and their contribution to the constraints on $\MH$. In addition, the current uncertainties of the theoretical predictions for $\MW$ and $\sweff$ due to missing higher order corrections are estimated and expectations and necessary theoretical improvements for future colliders are explored. The constraints from rare B decays are also discussed. Analysis of the present experimental and theoretical precisions yield a current upper bound on $\MH$ of $\sim 200$ GeV. Including anticipated improvements corresponding to the prospective situation at future colliders (Tevatron Run II, LHC, LC/GigaZ), we find a relative precision of about 25% to 8% (or better) is achievable in the indirect determination of $\MH$.

hep-ph↗
arXiv2001

Model-Independent Analysis of g_μ-2

Assuming that the scale of new physics exceeds the weak scale, we have considered all possible origins of deviations from the Standard Model in $\gmu2$. If the underlying theory can be treated perturbatively, then to account for an effect as large as has been recently reported\cite{BNL}, the only possibilities would be models that contain particles that yield direct contributions, of which SUSY models are prototypical, or models having unexpectedly light leptoquarks or having a rather exotic heavy vector boson that couples predominantly to muons. Other possibilities either are already excluded by existing experimental results or would have to be unnaturally large. If, on the contrary, the underlying new physics involves strong interactions, as in technicolor models, then the discrepancy could be accounted for by a variety of effective operators.

hep-ph↗
arXiv2001

Effective theory of systems coupled strongly to rapidly-varying external sources

We consider quantum systems which interact strongly with a rapidly varying environment and derive a Schrodinger-like equation which describes the time evolution of the average wave function. We show that the corresponding Hamiltonian can be taken to be Hermitian provided all states are rotated using an appropriate unitary transformation. The formalism is applied to a variety of systems and is compared and contrasted with related results describing stochastic resonances.

physics.gen-ph↗
arXiv2001

Proposing "b-Parity" - a New Approximate Quantum Number in Inclusive b-jet Production - as an Efficient Probe of New Flavor Physics

We consider the inclusive reaction \ell^+ \ell^- -> nb +X (n = number of b-jets) in lepton colliders for which we propose a useful approximately conserved quantum number b_P=(-1)^n that we call b-Parity (b_P). We make the observation that the Standard Model (SM) is essentially b_P-even since SM b_P-violating signals are necessarily CKM suppressed. In contrast new flavor physics can produce b_P=-1 signals whose only significant SM background is due to b-jet misidentification. Thus, we show that b-jet counting, which relies primarily on b-tagging, becomes a very simple and sensitive probe of new flavor physics (i.e., of b_P-violation).

hep-ph↗
arXiv1999

Flavor changing single top quark production channels at e^+e^- colliders in the effective Lagrangian description

We perform a global analysis of the sensitivity of LEP2 and e^+e^- colliders with a c.m. energy in the range 500 - 2000 GeV to new flavor-changing single top quark production in the effective Lagrangian approach. The processes considered are sensitive to new flavor-changing effective vertices such as Ztc, htc, four-Fermi tcee contact terms as well as a right-handed Wtb coupling. We show that e^+ e^- colliders are most sensitive to the physics responsible for the contact tcee vertices. For example, it is found that the recent data from the 189 GeV LEP2 run can be used to rule out any new flavor physics that can generate these four-Fermi operators up to energy scales of Λ> 0.7 - 1.4 TeV, depending on the type of the four-Fermi interaction. We also show that a corresponding limit of Λ> 1.3 - 2.5 and Λ> 17 - 27 TeV can be reached at the future 200 GeV LEP2 run and a 1000 GeV e^+e^- collider, respectively. We note that these limits are much stronger than the typical limits which can be placed on flavor diagonal four-Fermi couplings. Similar results hold for μ^+μ^- colliders and for tu(bar) associated production. Finally we briefly comment on the necessity of measuring all flavor-changing effective vertices as they can be produced by different types of heavy physics.

hep-ph↗
arXiv1998

R-parity violation and uses of the rare decay sneutrino-->gamma+gamma in hadron and photon colliders

We consider implications of the loop process sneutrino -> gamma gamma in the MSSM with R-parity violation for future experiments, where the sneutrino is produced as the only supersymmetric particle. We present a scenario for the R-parity violating couplings, where this clean decay, although rare with Br(sneutrino -> gamma gamma) ~ 10^{-6}, may be useful for sneutrino detection over a range of sneutrino masses at the LHC. Furthermore, the new sneutrino-gamma-gamma effective coupling may induce detectable sneutrino resonant production in gamma gamma collisions, over a considerably wide mass range. We compare sneutrino -> gamma gamma, gg throughout the paper with the analogous yet quantitatively very different, Higgs -> gamma gamma, gg decays and comment on the loop processes sneutrino -> WW, ZZ.

hep-ph↗
arXiv1998

Effective operator contributions to the oblique parameters

We present a model and process independent study of the contributions from non-Standard Model physics to the oblique parameters S, T and U. We show that within an effective lagrangian parameterization the expressions for the oblique parameters in terms of observables are consistent, while those in terms of the vector-boson vacuum polarization tensors are ambiguous. We obtain the constraints on the scale of new physics derived from current data on S, T and U and note that deviations in U from its Standard Model value would favor a scenario where the underlying physics does not decouple.

hep-ph↗
arXiv1997

Implications of a W^+W^- (ZZ) - Higgs - t c-bar$ Interaction for e^+e^- -> t c-bar ν_e ν_e-bar, t c-bar e^+ e^-, t c-bar Z and for t -> cW^+W^-, cZZ in a Two Higgs Doublet Model

The Standard Model with one extra Higgs doublet may give rise to enhanced TREE-LEVEL flavor-changing-scalar coupling of a neutral Higgs to a pair of top-charm quarks. This coupling may drive a large TREE-LEVEL effective W^+W^-(ZZ) - Higgs - t c-bar interaction. As a result we find that the reactions e^+e^- -> t c-bar ν_e ν_e-bar, t c-bar e^+ e^-, t c-bar Z and the two rare top decays t -> cW^+W^-, t -> cZZ become very sensitive probes of such an effective interaction. The most promising ones, e^+e^- -> t c-bar ν_e ν_e-bar, t c-bar e^+ e^-, may yield several hundreds and up to thousands of such events at the Next Linear Collider with a center of mass energy of \sqrt{s}=0.5 - 2 TeV if the mass of the lightest neutral Higgs is a few hundred GeV. The rare decays t -> cW^+W^- and t -> cZZ may be accessible at the LHC if the mass of the lightest neutral Higgs lies in the narrow window 150 GeV < m_h < 200 GeV.

hep-ph↗
arXiv1997

Probing the Flavor-Changing tc vertex via Tree-Level Processes: e+e- -> t bar-c nu_e bar-nu_e, t bar-c e+ e- and t -> c W+ W-

The reactions e+e- -> t bar-c nu_e bar-nu_e, t bar-c e+ e- are very sensitive probes of the flavor-changing-scalar couplings which can occur in a model with one extra Higgs doublet. At the Next Linear Collider, with a center of mass energy of sqrt{s}=0.5--2 TeV, several hundreds and up to thousands of such events may be produced if the mass of the light neutral Higgs is a few hundred GeV. We also briefly comment on the decays t -> c W+ W-, t -> c Z Z. All of these reactions are severely suppressed in the Standard Model

hep-ph↗
arXiv1997

The Thomas-Fermi approximation for gauge theories

An effective field approximation, similar to the atomic Thomas-Fermi approach, is proposed for studying non-Abelian gauge theories which includes finite-volume effects. As applications of the formalism the equation of state for an SU(2) gauge theory with massless fermions is obtained. The extensions to realistic situations are briefly discussed.

hep-ph↗
arXiv1996

Anomalous Gauge Boson Couplings

The measurement of anomalous gauge boson self couplings is reviewed for a variety of present and planned accelerators. Sensitivities are compared for these accelerators using models based on the effective Lagrangian approach. The sensitivities described here are for measurement of generic parameters kappa_v, lambda_v, etc., defined in the text. Pre-LHC measurements will not probe these couplings to precision better than O(1/10). The LHC should be sensitive to better than O(1/100), while a future NLC should achieve sensitivity of O(1/1000) to O(1/10000) for center of mass energies ranging from 0.5 to 1.5 TeV.

hep-ph↗