Supersymmetric extensions of the Standard Model with small R-parity and lepton number violating couplings are naturally consistent with primordial nucleosynthesis, thermal leptogenesis and gravitino dark matter. We consider supergravity models with universal boundary conditions at the grand unification scale, and scalar tau-lepton or bino-like neutralino as next-to-lightest superparticle (NLSP). Recent Fermi-LAT data on the isotropic diffuse gamma-ray flux yield a lower bound on the gravitino lifetime. Comparing two-body gravitino and neutralino decays we find a lower bound on a neutralino NLSP decay length, $c τ_{χ^0_1} \gsim 30 cm$. Together with gravitino and neutralino masses one obtains a microscopic determination of the Planck mass. For a stau-NLSP there exists no model-independent lower bound on the decay length. Here the strongest bound comes from the requirement that the cosmological baryon asymmetry is not washed out, which yields $c τ_{\tildeτ_1} \gsim 4 mm$. However, without fine-tuning of parameters, one finds much larger decay lengths. For typical masses, $m_{3/2} \sim 100 GeV$ and $m_{NLSP} \sim 150 GeV$, the discovery of a photon line with an intensity close to the Fermi-LAT limit would imply a decay length $cτ_{NLSP}$ of several hundred meters, which can be measured at the LHC.
We study unconventional decays of the top-quark in the framework of SUSY models with spontaneously broken R-parity. In particular we discuss an effective theory which consists of the MSSM plus bilinearly broken R-parity. We demonstrate that the decay modes t -> stau + b and t -> tau + sbottom can have large branching ratios even in scenarios where the tau-neutrino mass is very small. We show that existing Tevatron data already probe the theoretical parameters, with promising prospects for further improvement at the Run 2 of the Tevatron.
The simplest gauge theories for the conservation of R-parity in supersymmetry are discussed. We show how the minimal theory based on the B-L gauge symmetry predicts that R-parity must be spontaneously broken at the TeV scale. The most striking signals of these theories at the Large Hadron Collider are discussed. We present a realistic theory where the local baryon and lepton numbers are spontaneously broken at the supersymmetry breaking scale. The possibility to understand the conservation of R-parity in grand unified theories defined in four dimensions is mentioned.
We study gauge and Yukawa coupling unification in the simplest extension of the Minimal Supersymmetric Standard Model (MSSM) which incorporates R-Parity violation through a bilinear superpotential term. Contrary to what happens in the MSSM, we show that bottom-tau unification at the scale M_GUT where the gauge couplings unify can be achieved for any value of tan(beta) by choosing appropriately the sneutrino vacuum expectation value. In addition, we show that bottom-tau-top unification occurs in a slightly wider tan(beta) range than in the MSSM.
We determine new constraints on the products of two R-parity violating coupling constants from the NOMAD and CHORUS experiments on nu_mu --> nu_tau oscillations. We obtain improved results from (a) lepton flavour violating (LFV) meson decays, (b) LFV deep-inelastic scattering and (c) a combination of the two.
We study the pattern of gluino cascade decays in a class of supersymmetric models where R-parity is spontaneously broken. The multi-lepton and same-sign dilepton rates in these models are compared with those of the Minimal Supersymmetric Standard Model. We show that these rates can be substantially enhanced in models with broken R-parity.
If the Lagrangian of nature respects parity invariance then there are two distinct possibilities: either parity is unbroken by the vacuum or it is spontaneously broken. We examine the two simplest phenomenologically consistent gauge models which have unbroken and spontaneously broken parity symmetries, respectively. These two models have a Lagrangian of the same form, but a different parameter range is chosen in the Higgs potential. They both predict the existence of dark matter and can explain the MACHO events. However, the models predict quite different neutrino physics. Although both have l…
We review models where R-parity is broken, either spontaneously or explicitly. In this last case we consider the situation where R-parity is broken via bilinear terms in the superpotential. We show that although at tree level only one neutrino gets mass, at one--loop level all three neutrinos became massive. We study the conditions under which bimaximal mixing can be achieved and show that the masses can be in the correct ranges needed for solving the atmospheric and solar neutrino problems.
We review the consequences of spontaneously broken R-parity in present and planned lepton-lepton colliders. In the left-right models the R-parity, $R=(-1)^{3(B-L)+2S}$, is preserved due to the gauge symmetry, but it must be spontaneously broken in order to the scalar spectrum to be physically consistent. The spontaneous breaking is generated via a non-vanishing VEV of at least one of the sneutrinos, which necessarily means non-conservation of lepton number $L$. The R-parity violating couplings are parametrized in terms of mixing angles, whose values depend on model parameters. Combined with th…
Investigating leptonic decays of pi^-, K^-, B^-, pi^0, K_L^0, B_s^0 we present new bounds on some products of two R-parity violating coupling constants. For mesons of a similar structure but so far poor experimental data we give the corresponding formulae, to be used in the future.
Unified models incorporating the right handed neutrino in a symmetric way generically possess parity symmetry. If this is broken spontaneously it results in the formation of domain walls in the early Universe, whose persistence is unwanted. A generic mechanism for destabilisation of such walls is a small pressure difference signalled by difference in the free energy across the walls. It is interesting to explore the possibility of such effects in conjunction with the effects that break supersymmetry in a phenomenologically acceptable way. Realising this possibility in the context of several sc…
The solar and atmospheric neutrino anomalies constitute the only solid and most remarkable evidence for physics beyond the Standard Model, indicating that the lepton mixing matrix is fundamentally distinct from that describing the quarks. Here I will report on how supersymmetry with spontaneously or bilinearly broken R Parity provides a predictive theory for neutrino mass and mixing which leads to a solution of neutrino anomalies which can be clearly tested at high energy accelerators.
A small breaking of R-parity reconciles thermal leptogenesis, gravitino dark matter and primordial nucleosynthesis. We find that the same breaking relaxes cosmological bounds on the axion multiplet. Naturally expected spectra become allowed and bounds from late particle decays become so weak that they are superseded by bounds from non-thermal axion production. In this sense, the strong CP problem serves as an additional motivation for broken R-parity.
The simplest unified extension of the Minimal Supersymmetric Standard Model with bilinear R-Parity violation provides a predictive scheme for neutrino masses which can account for the observed atmospheric and solar neutrino anomalies. Despite the smallness of neutrino masses R-parity violation is observable at present and future high-energy colliders, providing an unambiguous cross-check of the model.
We study the pair production of charginos in e+e- collisions followed by the decay via R-parity violating LQD operators. We determine the complete matrix element squared for chargino decays via LQD or LLE operators. We find regions in MSSM parameter space where the chargino mass is 52.5GeV and the R-parity violating decays of the charginos dominate the gauge decays to neutralinos. At LEP2 this then leads to additional 4 jet events which could explain the excess recently observed by ALEPH.
The R parity odd renormalizable Yukawa interactions of quarks and leptons with the scalar superpartners have the ability to violate the baryon and lepton numbers, change the hadron and lepton flavors and make the lightest supersymmetric particle unstable. The existence of an approximate R parity symmetry would thus affect in a deep way the conventional framework of the Minimal Supersymmetric Standard Model where an exact R parity symmetry is built-in by assumption. The purpose of the present review is to survey in a systematic way the direct experimental constraints set on the R parity violati…
The Higgs sector in spontaneously broken R Parity supersymmetry (RPSUSY) shows interesting features that require new search techniques. Both the mass spectrum and production rates may differ from the standard model and minimal supersymmetric model (MSSM) expectations. For some parameter choices, the dominant Higgs boson decay mode can even be invisible, leading to events with large missing transverse momentum carried by superweakly interacting majorons. We study the reaction $pp \ra Z + H + X$, and find that it canlead to detectable events at LHC/SSC for a large region of parameter space.
Supersymmetric models with broken R-parity induced by lepton number violating terms provide a calculable framework for neutrino masses and mixings. Within models with bilinear R-parity breaking six new physical phases appear which are potential sources of novel CP-violating phenomena compared to the minimal supersymmetric extension of the standard model. We consider CP-violating observables in the decays of the lightest supersymmetric particle in this class of models. We show that: (i) Neutrino physics requires a strong correlation between three different pairs of phases, thus reducing the eff…
In a class of supersymmetric models with R-parity breaking the lightest stop can have new decay modes into third generation fermions, $\tilde{t}_1 \rightarrow b + τ$. We show that this decay may be dominant or at least comparable to the ordinary R-parity conserving mode $\tilde{t}_1 \rightarrow c + \tildeχ_1^0$, where $\tildeχ_1^0$ denotes the lightest neutralino. The new R-parity violating decay mode could provide new signatures for stop production at LEP.
Lepton-flavor-violating decays of the type L->l gamma gamma (mu->e gamma gamma, tau->e gamma gamma, and tau->mu gamma gamma) are proposed as new probes of R-parity-violating supersymmetry. Non-penguin diagrams with a sneutrino that decays into two photons via a triangle graph might trigger such decays even in the absence of the corresponding radiative decays into one photon only, e.g. mu->e gamma. Thus, processes of the type L->l gamma gamma may provide an independent probe of new flavor physics.
We propose a simple renormalizable left-right theory where R-parity is spontaneously broken and neutrino masses are generated through the Type I seesaw mechanism and R-parity violation. In this theory R-parity and the gauge symmetry are broken by the sneutrino vacuum expectation values and there is no Majoron problem. The SU(2)_R and R-parity violation scales are determined by the SUSY breaking scale making the model very predictive. We discuss the spectrum and possible tests of the theory through the neutralinos, charginos, Z^' and W_R decays at the Large Hadron Collider.
Higgs production from $Z$ decay in supersymmetry with spontaneous broken R parity proceeds mostly by the Bjorken process as in the standard model. However, the corresponding production rates can be weaker than in the standard model (SM), especially in the low mass region. This will substantially weaken the Higgs boson mass limits derived from LEP1. More strikingly, the main Higgs decay channel is "invisible", over most of the mass range accessible to LEP1, leading to events with large missing energy carried by majorons. This possibility should be taken into account in the planning of Higgs bos…
Domain wall structure which may form in theories with spontaneously broken parity is generically in conflict with standard cosmology. It has been argued that Planck scale suppressed effects can be sufficient for removing such domain walls. We study this possibility for three specific evolution scenarios for the domain walls, with evolution during radiation dominated era, during matter dominated era, and that accompanied by weak inflation. We determine the operators permitted by the supergravity formalism and find that the field content introduced to achieve desired spontaneous parity breaking …
We give an analytical calculation of solar neutrino masses and mixing at one-loop order within bilinear R-parity breaking supersymmetry, and compare our results to the exact numerical calculation. Our method is based on a systematic perturbative expansion of R-parity violating vertices to leading order. We find in general quite good agreement between approximate and full numerical calculation, but the approximate expressions are much simpler to implement. Our formalism works especially well for the case of the large mixing angle MSW solution (LMA-MSW), now strongly favoured by the recent KamLA…
Four different supersymmetric models based on SU(2)_L X U(1)_R X U(1)_B-L and SU(2)_L X SU(2)_R X U(1)_B-L gauge symmetry groups are studied. U(1)_B-L symmetry is broken spontaneously by a vacuum expectation value (VEV) of a sneutrino field. The right-handed gauge bosons may obtain their mass solely by sneutrino VEV. The physical charged lepton and neutrino are mixtures of gauginos, higgsinos and lepton interaction eigenstates. Explicit formulae for masses and mixings in the physical lepton fields are found. The spontaneous symmetry breaking mechanism fixes the trilinear R-parity breaking coup…
Scenarios with gravitino dark matter face potential cosmological problems induced by the presence of the Next-to-Lightest Supersymmetric Particle (NLSP) at the time of Big Bang Nucleosynthesis (BBN). A very simple, albeit radical, solution to avoid all these problems consists on assuming that R-parity is slightly violated, since in this case the NLSP decays well before the onset of BBN. Remarkably, even if the gravitino is no longer stable in this scenario, it still constitutes a very promising dark matter candidate. In this talk we review the motivations for this scenario and we present a mod…
In models with gauge mediated supersymmetry breaking the gravitino is the lightest supersymmetric particle. If R-parity is violated the gravitino decays, but with a half-live far exceeding the age of the universe and thus is, in principle, a candidate for the dark matter. We consider the decays of the next-to-lightest supersymmetric particle, assumed to be the neutralino. We show that in models where the breaking of R-parity is bilinear, the condition that R-parity violation explains correctly the measured neutrino masses fixes the branching ratio of the decay ${\tilde χ}^0_1 \to {\tilde G}γ$ …
The possible phenomenological consequences of R-parity violating interactions in the framework of low energy supersymmetry breaking are studied. It is pointed out that even very weak R-parity violation would completely overshadow one of the basic signatures of low energy supersymmetry breaking models, that is, the decay of the next to lightest supersymmetric particle into a photon (lepton) and missing energy. Thus, the observation of these decays would put very strong limits on R-parity violating couplings. Vice-versa, if R-parity violation is established experimentally, before a detailed know…
In a supersymmetric model where R-Parity and lepton number are violated bilinearly in the superpotential, which can explain the solar and atmospheric neutrino problems, we study the unification of gauge and Yukawa couplings at the GUT scale. We show that bottom-tau Yukawa coupling unification can be achieved at any value of $\tanβ$, and that the strong coupling constant prediction from unification of gauge couplings is closer to the experimental value compared with the MSSM. We also study the predictions for $V_{cb}$ in a Yukawa texture ansätze.
We present a simple theory where baryon and lepton numbers are spontaneously broken at the supersymmetry scale. In this context R-parity must be spontaneously broken but the theory still contains a stable field which can play the role of the cold dark matter of the Universe. We discuss the spectrum of the theory, the properties of the dark matter candidate and the predictions for direct detection experiments. This theory provides a concrete example of exotic supersymmetric signatures associated with having the simultaneous presence of R-parity violating and missing energy signals at the Large …
We present a simple analysis that allows us to extract the leading mass dependence of the dipole moment of matter fermions that might be induced by new physics. We present explicit results for the supersymmetric model with broken R-parity as an illustration. We show that the extra contributions to the electric dipole moment (edm) of fermions from R-parity violating interactions can occur only at two loop level, contrary to claims in the literature. We further find that unlike the generic lepto-quark models, the extra contributions to the dipole moments of the leptons can only be enhanced by m_…
We reconsider the possible presence of charge and colour breaking minima in the scalar potential of the minimal supersymmetric standard model (MSSM) and its minimal generalization with R-parity explicitly broken by bilinear terms (RMSSM). First we generalize some results previously derived for the MSSM case. Next we investigate how robust is the MSSM against its RMSSM extension. We examine the constraints on the RMSSM parameter space that follow from the required absence of charge breaking minima in the scalar potential. We point out the possibility of generating non--zero vacuum expectation v…
The gravitino is a promising supersymmetric dark matter candidate, even without strict R-parity conservation. In fact, with some small R-parity violation, gravitinos are sufficiently long-lived to constitute the dark matter of the universe, while the resulting cosmological scenario is consistent with primordial nucleosynthesis and the high reheating temperature needed for thermal leptogenesis. Furthermore, in this scenario the gravitino is unstable and might thus be accessible by indirect detection via its decay products. We compute in this thesis the partial decay widths for the gravitino in …
R parity violation can induce mixing of the supersymmetric Higgs bosons with the sneutrinos at the tree level. We study the effect of this mixing on the decays of Higgs scalars as well as sneutrinos in an effective model where the violation of R parity is included in the minimal supersymmetric model through bilinear lepton number violating superpotential terms. We show that a small violation of R parity can lead to a sizeable branching ratio for the supersymmetric Higgs boson decay mode $H \to χ\ell$ (where $χ$ denotes an electroweak gaugino and $\ell$ is either a tau neutrino or a tau lepton)…
We discuss the phenomenology of the lightest stop in models where R-parity is broken by bilinear superpotential terms. In this class of models we consider scenarios where the R-parity breaking two-body decay ~t_1->τ^+b competes with the leading three-body decays such as ~t_1->W^+b~χ^0_1. We demonstrate that the R-parity violating decay can be sizable and in some parts of the parameter space even the dominant one. Moreover we discuss the expectations for t_1->μ^+b and ~t_1->e^+b. The recent results from solar and atmospheric neutrinos suggest that these are as important as the tau bottom mode. …
Supersymmetric theories with an R-parity generally yield a striking missing energy signature, with cascade decays concluding in a neutralino that escapes the detector. In theories where R-parity is broken the missing energy is replaced with additional jets or leptons, often making traditional search strategies ineffective. Such R-parity violation is very constrained, however, by resulting B and L violating signals, requiring couplings so small that LSPs will decay outside the detector in all but a few scenarios. In theories with additional matter fields, R-parity can be broken collectively, su…
We study the mass spectra, production and decay properties of the lightest supersymmetric CP-even and CP-odd Higgs bosons in models with spontaneously broken R-parity (SBRP). We compare the resulting mass spectra with expectations of the Minimal Supersymmetric Standard Model (MSSM), stressing that the model obeys the upper bound on the lightest CP-even Higgs boson mass. We discuss how the presence of the additional scalar singlet states affects the Higgs production cross sections, both for the Bjorken process and the "associated production". The main phenomenological novelty with respect to th…
The contribution from the R parity violating interactions in the associated production of a top quark with a charm antiquark is examined for high energy leptonic colliders. We concentrate on the reactions associated with the semileptonic top decay. A set of characteristic dynamical distributions for the signal events is evaluated and the results contrasted against those from the standard model W-boson pair production background. Next, we turn to a study of a CP-odd observable, associated with the top spin, which leads to an asymmetry in the energy distribution of the emitted charged leptons fo…
Spontaneous violation of R parity can induce rare single photon decays of the $Z^0$ involving the emission of (nearly) massless pseudoscalar Goldstone bosons, majorons, as well as massive CP even or CP odd spin zero bosons that arise in the electroweak breaking sector of these models. We show that the majoron emitting decays can have a sizeable branching ratio of $10^{-5}$ or so, without conflicting any experimental observation from neutrino physics or particle searches. These decays may lead to interesting structures for the single photon spectrum involving either mono chromatic photons as we…
The Higgs boson may decay mainly to an invisible mode characterized by missing energy, instead of the Standard Model channels. This is a generic feature of many models where neutrino masses arise from the spontaneous breaking of ungauged lepton number at relatively low scales, such as spontaneously broken R-parity models. Taking these models as framework, we reanalyze this striking suggestion in view of the recent data on neutrino oscillations that indicate non-zero neutrino masses. We show that, despite the smallness of neutrino masses, the Higgs boson can decay mainly to the invisible Goldst…
In the present paper we have developed a concept of parallel ordinary (O) and mirror (M) worlds. We have shown that in the case of a broken mirror parity (MP), the evolutions of fine structure constants in the O- and M-worlds are not identical. It is assumed that E_6-unification inspired by superstring theory restores the broken MP at the scale \sim 10^{18} GeV, what unavoidably leads to the different E_6-breakdowns at this scale: E_6 \to SO(10)\times U(1)_Z - in the O-world, and E'_6 \to SU(6)'\times SU(2)'_Z - in the M-world. Considering only asymptotically free theories, we have presented t…
We have examined in detail the nonrestoration of symmetry at high temperature in a finite-temperature Littlest Higgs model, without and with T-parity, by evaluating the one-loop-order finite-temperature integrals of the effective potential numerically, without the high-temperature approximation, We observe that in the model without T-parity it is not possible to find a transition temperature within the allowed temperature range of the model (0<T<4f) if the UV completion factors are those which give the Standard Model electroweak minimum, as the effective potential always increases with tempera…
We review supersymmetry models with and without R-parity. After briefly describing the Minimal Supersymetric Standard Model and its particle content we move to models where R-parity is broken, either spontaneously or explicitly. In this last case we consider the situation where R-parity is broken via bilinear terms in the superpotential. The radiative breaking of these models is described in the context of $b$--$τ$ and $b$--$τ$--$t$ unification. Finally we review the phenomenology of these R-parity violating models.
The straightforward supersymmetrization of the Standard Model (SM) results in a phenomenologically inconsistent theory in which Baryon number ($B$) and Lepton number ($L$) are violated by dimension 4 operators, inducing fast proton decay. Proton stability allows only for separate $L$ or $B$ violation and, if neutrinos are massive Majorana particles, $L$ violating terms must be present. In this thesis I will study a Supersymmetric Standard Model (SSM) realization with $B$ conservation and minimal $L$ violation. In this framework $L$ is mildly violated only by super-renormalizable terms, allowin…
We study the pattern of gluino cascade decays in a class of supersymmetric models where R-parity is spontaneously broken. We give a detailed discussion of the R-parity violating decays of the lightest neutralino, the second lightest neutralino and the lightest chargino. The multi-lepton and same-sign dilepton signal rates expected in these models are compared with those predicted in the Minimal Supersymmetric Standard Model. We show that these rates can be substantially enhanced in broken R-parity models.
We examine the effects of the R parity odd renormalizable interactions on flavor changing rates and CP violation asymmetries in the production of fermion-antifermion pairs at $e^-- e^+$ leptonic colliders. The produced fermions may be leptons, down-quarks or up-quarks, and the center of mass energies may range from the Z-boson pole up to $ 1000$ GeV. Off the Z-boson pole, the flavor changing rates are controlled by tree level amplitudes and the CP asymmetries by interference terms between tree and loop level amplitudes. At the Z-boson pole, both observables involve loop amplitudes. The lepton …
We examine the effect of the R parity odd renormalizable interactions on flavor non-diagonal rates and CP violation asymmetries in the production of slepton pairs at $e^- - e^+$ leptonic colliders, for center of mass energies spanning the interval from the Z-boson pole up to 1000 GeV. The lepton number violating interactions, associated with the lepton number violating coupling constants, are assumed to incorporate CP odd complex phases. The flavor changing rates are controlled by tree level amplitudes and quadratic products of different R parity violating coupling constants and the CP asymmet…
We point out that axino can be a natural candidate for sterile neutrino which would accommodate the LSND data with atmospheric and solar neutrino oscillations. It is shown that the so called 3+1 scheme can be easily realized when supersymmetry breaking is mediated by gauge interactions and also R-parity is properly broken. Among the currently possible solutions to the solar neutrino problem, only the large angle MSW oscillation is allowed in this scheme. The weak scale value of the Higgs $μ$ parameter and the required size of R-parity violation can be understood by means of spontaneously broke…
The excess of high $Q^2$ events at HERA reported in the early 1997 by H1 and ZEUS collaborations has become the subject of extensive studies in the framework of several models related to new physics. Here we concentrate on the most promising, from our point of view, model describing HERA anomaly. We update our previous analysis and take into account new HERA statistics of the 1997 year. HERA events are considered within the R-parity broken SUSY model for a specific scenario with several non-zero couplings. R-parity broken SUSY with several non-zero couplings could explain both high $Q^2 e^+ + …
We consider tree-level corrections to hypercharge changing semileptonic decays of certain baryons induced by a minimal supersymmetric standard model with explicitly broken R-parity via $L$-violation. This study leads to a new set of constraints on the products of couplings arising from the LQd$^c$ operator of the superpotential.
We point out that, if R-parity is broken spontaneously, the neutralino can decay to the final state majoron plus neutrino, which from the experimental point of view is indistinguishable from the standard missing momentum signal of supersymmetry. We identify the regions of parameter space where this decay mode is dominant and show that they are independent of R-parity conserving SUSY parameters. Thus, (a) only very weak limits on R-parity violating couplings can be derived from the observation of missing momentum events and (b) at future collider experiments huge statistics might be necessary t…
We report on the recently proposed joint resolution of two long-standing puzzles in weak radiative (WR) and nonleptonic (NL) hyperon decays (HD). First, a good VMD-based description of WRHD is presented. In particular, the large negative asymmetry observed in the Σ^+ \to p γdecay is explained through a calculably large SU(3)-breaking effect in the relevant parity-violating amplitude. Second, the achieved description of the parity-violating WRHD amplitudes permits the extraction, via the SU(2)_W + VMD route, of the non-soft-pion correction term in the parity-violating NLHD amplitudes. The latte…
We discuss the possible signatures at the Large Hadron Collider in models where R-parity is spontaneously broken. In the context of the minimal gauge theory for R-parity, we investigate signals with multileptons which can provide an unique test of this theory. The possible impact of these ideas for the search of supersymmetry at the Large Hadron Collider is discussed. We also discuss the constraints coming from cosmology due to the existence of two light sterile neutrinos in the theory.
We study a simple extension of the minimal supersymmetric Standard Model in which the Abelian sector of the theory consists of B-L and right-handed isospin. In the minimal model this Abelian gauge structure is broken to the standard model hypercharge gauge group by non-vanishing vacuum expectation values of the right-handed sneutrinos, resulting in spontaneous R-parity violation. This theory can emerge as a low energy effective theory of a left-right symmetric theory realized at a high scale. We determine the mass spectrum of the theory, and discuss the generation of neutrino masses and R-pari…
We investigate supersymmetric models where neither R-parity nor lepton number nor baryon number is imposed. The full high energy theory has an exact horizontal U(1) symmetry that is spontaneously broken. Quarks and Higgs fields carry integer horizontal charges but leptons carry half integer charges. Consequently, the effective low energy theory has two special features: a U(1) symmetry that is explicitly broken by a small parameter, leading to selection rules, and an exact residual Z_2 symmetry, that is lepton parity. As concerns neutrino parameters, the Z_2 symmetry forbids contributions from…
We have studied the predictions for the LSP decay within the framework of a radiatively broken unified supergravity model without R-parity. Assuming that Higgs/slepton mixing is the only source of R-parity breaking and responsible for the observed neutrino oscillations we obtain predictons for the LSP life-time and branching fractions.
Testing whether data breaks symmetries of interest can be important to many fields. This paper describes a simple way that machine learning algorithms (whose outputs have been appropriately symmetrised) can be used to detect symmetry breaking. The original motivation for the paper was an important question in Particle Physics: "Is parity violated at the LHC in some way that no-one has anticipated?" and so we illustrate the main idea with an example strongly related to that question. However, in order that the key ideas be accessible to readers who are not particle physicists but who are intere…
Charge conjugation (C) and Parity (P) are exact symmetries at theta =pi and Theta = mu/(iT)=pi, where theta is the parameter of the so-called theta-vacuum, mu is the imaginary quark-number chemical potential and T is the temperature. Spontaneous breakings of these discrete symmetries are investigated by the the Polyakov-loop extended Nambu--Jona-Lasinio (PNJL) model. At zero T, P symmetry is spontaneously broken while C symmetry is conserved. As T increases, P symmetry is restored just after C symmetry is spontaneously broken, so that either P or C symmetry or both the symmetries are spontaneo…
We search for a direction in the sky that exhibits parity symmetry under reflections through a plane. We use the natural estimator, which compares the power in even and odd $\ell+m$ multipoles, and apply minimal blind masking of outliers to the ILC map in order to avoid large errors in the reconstruction of multipoles. The multipoles of the cut sky are calculated both naively and by using the covariance inversion method and we estimate the significance of our results using $Λ$CDM simulations. Focusing on low multipoles, $2\leq \ell \leq \ell_{\max}$ with $\ell_{\max}=5,6$ or even 7, we find tw…
We find that spontaneously broken parity (P) or left-right symmetry stabilizes dark matter in a beautiful way. If dark matter has a non-real intrinsic parity \pm i (e.g. Majorana fermions), parity can ensure that it cannot decay to all normal particles with real intrinsic parities. However if Majorana couplings are absent either in the Lepton or the dark sector, P symmetry can be redefined to remove relative non-real intrinsic phases. It is therefore predicted that neutrinos and dark matter fermions must have Majorana masses if dark matter is stable due to parity. We also consider vectorlike d…
We examine the effects of R-parity violating (RPV) supersymmetry on the two-photon B decays B -> X_s gamma gamma and B_s -> gamma gamma. We find that, although there are many one-loop RPV diagrams that can contribute to these two-photon B decays, the RPV effect is dominated by a single diagram. This diagram, named here lambda-irreducible, has a distinct topology which is irrelevant for the b -> s gamma amplitude at one-loop and has thus a negligible effect on the one-photon decay B -> X_s gamma. We show that the lambda-irreducible RPV diagram can give BR(B_s -> gamma gamma) ~ 5*10^(-6) and BR(…
