In order to explain the results in Eq.(l) one needs to go to a theory beyond the standard model (... more In order to explain the results in Eq.(l) one needs to go to a theory beyond the standard model (SM). Supersymmetry(SUSY) is an interesting possibility for new physics at TeV scale. There have been several proposals in recent times which attempt to explain the experimental data on neutrinos in the context of minimal supersymmetric standard model (MSSM) with bilinear and trilinear R-parity violation [2-4]. Due to R-parity violation the lightest supepparticle (LSP) is unstable forthis class ofmodels. However MSSM possesses the so-called "p-pioblem" l5l. related to the bilineart et^ p A, H in the MSSM superpotential. One ofthe solutions to The experimental results on neutrinos provide evidence of non-zero neutrino masses and mixing aneles. In this work we examine in detail the neulrino mass patterns and mixing angles in an extension of the minimal supersymmetiic standard model with three gauge-singlet neutrinos and R-parity violarion. The Majorana maises for the gauge-singlet neutrinos as well as the usual p-term for the Higgs Superfields are generated atthe electroweak scale through the vacuum expectation values ofthe singlet 6 n"rt.inor. The resulting effective mass matrix for the three light neutrinos have contributions from the seesaw mechanism involving the singlet neutrinos as well as due to the mixing with the heaq neutralinos. We show that evin with flavour diagonal neutrino Yukawa couplings the global data on three-flavour neutrinos can be well accounted for in this scenario at the tree level. We further study the decays ofthe lightest neutralino in this model. The lightest neutralino can be the lightest supersymmetric particte pSf;. We focus on different cases where the Iightest neutralino is either a bino or a higgsino or a gauge-singlei neutrino. We study the important phenomenological differences between these cases and find"out th"at certain ratios ofdecay branching ratios ofthe lightest neutralino are correlated with eitherthe solarorthe atmospheric (and reactor) neutrino angle. Neutrino oscillation experiments have confirmed nonzero masses and mixing-angles for neutrinos. Various experiments suggest that the mixing pattem of the three light neutrinos is bilarge, that isto say there are two large mixing angles and one small mixing angle. The data can be explained very well with the following set of mass squared differences and mixing angles at 3o c.L. ul 7.05 x 1o 5ev2 < Lml, ! 8.34 x 1o 5ev2, 2.07 x 10-3ev2 S Al-3r1 5, 2.75 x 10-3ev2, 30.39" I drz <37.46', 36.87' 51zt < 54.94", d13 < 13.69", (1) where L.m!, = mf; ml.
New data on the lepton mixing angle θ_13 imply that the eμ element of the matrix m_ν m_ν^†, where... more New data on the lepton mixing angle θ_13 imply that the eμ element of the matrix m_ν m_ν^†, where m_ν is the neutrino Majorana mass matrix, cannot vanish. This implies a lower limit on lepton flavor violating processes in the eμ sector in a variety of frameworks, including Higgs triplet models or the concept of minimal flavor violation in the lepton sector. We illustrate this for the branching ratio of μ→ e γ in the type II seesaw mechanism, in which a Higgs triplet is responsible for neutrino mass and also mediates lepton flavor violation. We also discuss processes like μ→ ee̅e and μ→ e conversion in nuclei. Since these processes have sensitivity on the individual entries of m_ν, their rates can still be vanishingly small.
The "μ from ν" supersymmetric standard model (μνSSM) can accommodate the newly discover... more The "μ from ν" supersymmetric standard model (μνSSM) can accommodate the newly discovered Higgs-like scalar boson with a mass around 125 GeV. This model provides a solution to the μ-problem and simultaneously reproduces correct neutrino physics by the simple use of right-handed neutrino superfields. These new superfields together with the introduced R-parity violation can produce novel and characteristic signatures of the μνSSM at the LHC. We explore the signatures produced through two-body Higgs decays into the new states, provided that these states lie below in the mass spectrum. For example, a pair produced light neutralinos depending on the associated decay length can give rise to displaced multi-leptons/taus/jets/photons with small/moderate missing transverse energy. In the same spirit, a Higgs-like scalar decaying to a pair of scalars/pseudoscalars can produce final states with prompt multi-leptons/taus/jets/photons.
The ATLAS and CMS collaborations have recently released their new analyses of the diphoton search... more The ATLAS and CMS collaborations have recently released their new analyses of the diphoton searches. We look in detail the consequences of their results deriving strong constraints on models where a scalar resonance s decays into two light pseudoscalars which in turn decay into two pairs of collimated photons, mis-identified with two real photons. In our construction, all mass terms are generated dynamically, and only one pair of vector-like fermions generate couplings which will be probed using the upcoming LHC data. Moreover, we show that a stable dark matter candidate, respecting the cosmological constraints, is naturally affordable in the model.
In this work, we investigate the phenomenological consequences of a doubly charged scalar which m... more In this work, we investigate the phenomenological consequences of a doubly charged scalar which may belong to different uncoloured scalar multiplets. This doubly charged scalar couples to the charged leptons as well as gauge bosons, which we parametrize in a model independent way. Restricting ourselves in the regime of conserved charged-parity (CP), we assume only a few non-zero Yukawa couplings (y_μℓ, where ℓ=e,μ,τ) between the doubly charged scalar and the charged leptons. Our choices allow the doubly charged scalar to impinge low-energy processes like anomalous magnetic moment of muon and a few possible charged lepton flavour violating (CLFV) processes. These same Yukawa couplings are also instrumental in producing same-sign dilepton signatures at the LHC. In this article we examine the impact of individual contributions from the diagonal and off-diagonal Yukawa couplings in the light of muon (g-2) excess. Subsequently, we use the derived information to inquire the possible CLFV ...
We investigate signatures induced by a very light pseudoscalar Higgs in neutralino decays in the ... more We investigate signatures induced by a very light pseudoscalar Higgs in neutralino decays in the Next-to-Minimal Supersymmetric Standard Model (NMSSM) and determine their observability at the LHC. We concentrate on scenarios which feature two light scalar Higgs bosons (one of them is SM-like with a mass of 125 GeV and a singlet-like lighter one) with a very light (singlet-like) pseudoscalar Higgs in the mass range 2m_tau < m_a1 < 2m_b. We consider neutralino-chargino pair production and the subsequent decay X_2,3-> X_1 a1, which leads to topologies involving multi-leptons and missing transverse energy. We determine a set of selection cuts that can effectively isolate the signal from backgrounds of the Standard Model or the Minimal Supersymmetric Standard Model. We also exemplify the procedure with a set of benchmark points, for which we compute the expected number of events and signal strength for LHC with 8 TeV center of mass energy. We show that this signal can already be...
We investigate signatures of the minimal supersymmetric inverse seesaw model at the large hadron ... more We investigate signatures of the minimal supersymmetric inverse seesaw model at the large hadron collider (LHC) with three isolated leptons and large missing energy (3\ell + \mET or 2\ell + 1\tau + \mET, with \ell=e,\mu) in the final state. This signal has its origin in the decay of chargino-neutralino (\chpm1\ntrl2) pair, produced in pp collisions. The two body decays of the lighter chargino into a charged lepton and a singlet sneutrino has a characteristic decay pattern which is correlated with the observed large atmospheric neutrino mixing angle. This correlation is potentially observable at the LHC by looking at the ratios of cross sections of the trilepton + \mET channels in certain flavour specific modes. We show that even after considering possible leading standard model backgrounds these final states can lead to reasonable discovery significance at the LHC with both 7 TeV and 14 TeV center-of-mass energy.
In this article we propose a simultaneous collider search strategy for a pair of scalar bosons in... more In this article we propose a simultaneous collider search strategy for a pair of scalar bosons in the NMSSM through the decays of a very light pseudoscalar. The massive scalar has a mass around 126 GeV while the lighter one can have a mass in the vicinity of 98 GeV (thus explaining an apparent LEP excess) or be much lighter. The successive decay of this scalar pair into two light pseudoscalars, followed by leptonic pseudoscalar decays, produces clean multi-lepton final states with small or no missing energy. Furthermore, this analysis offers an alternate leptonic probe for the 126 GeV scalar that can be comparable with the ZZ* search channel. We emphasize that a dedicated experimental search for multi-lepton final states can be an useful probe for this scenario and, in general, for the NMSSM Higgs sector. We illustrate our analysis with two representative benchmark points and show how the LHC configuration with 8 TeV center-of-mass energy and 25 inverse femtobarns of integrated lumi...
Nonstandard on-shell decays of W^± and Z bosons are possible within the framework of extended sup... more Nonstandard on-shell decays of W^± and Z bosons are possible within the framework of extended supersymmetric models, i.e., with singlet states and/or new couplings compared to the minimal supersymmetric standard model. These modes are typically encountered in regions of the parameter space with light singlet-like scalars, pseudoscalars, and neutralinos. In this letter we emphasize how these states can lead to novel signals at colliders from Z- or W^±-boson decays with prompt or displaced multileptons/tau jets/jets/photons in the final states. These new modes would give distinct evidence of new physics even when direct searches remain unsuccessful. We discuss the possibilities of probing these new signals using the existing LHC run-I data set. We also address the same in the context of the LHC run-II, as well as for the future colliders. We exemplify our observations with the "μ from ν" supersymmetric standard model, where three generations of right-handed neutrino superfie...
Both the ATLAS and CMS collaborations have recently observed an excess in the di-photon invariant... more Both the ATLAS and CMS collaborations have recently observed an excess in the di-photon invariant mass distribution in the vicinity of 750 GeV with a local significance of 3 . In this article we try to investigate this excess in the context of a minimal simplified framework assuming e ective interactions of the hinted resonance with photons and gluons. We scrutinise the consistency of this observation with possible accompanying yet hitherto unseen signatures of this resonance. Subsequently, we try to probe the nature of new particles, e.g., spin, electric charge and number of colour, etc., that could remain instrumental to explain this excess through loop-mediation.
In this thesis we try to discuss certain phenomenological aspects of an R-parity violating non-mi... more In this thesis we try to discuss certain phenomenological aspects of an R-parity violating non-minimal supersymmetric model, called $\mu\nu$SSM. We show that $\mu\nu$SSM can provide a solution to the $\mu$-problem of supersymmetry and can simultaneously accommodate the existing three flavour global data from neutrino experiments even at the tree level with the simple choice of flavour diagonal neutrino Yukawa couplings. We show that it is also possible to achieve different mass hierarchies for light neutrinos at the tree level itself. In $\mu\nu$SSM, the effect of R-parity violation together with a seesaw mechanism with TeV scale right-handed neutrinos are instrumental for light neutrino mass generation. We also analyze the stability of tree level neutrino masses and mixing with the inclusion of one-loop radiative corrections. In addition, we investigate the sensitivity of the one-loop corrections to different light neutrino mass orderings. Decays of the lightest supersymmetric part...
We analyze relevant signals expected at the LHC for a left sneutrino as the lightest supersymmetr... more We analyze relevant signals expected at the LHC for a left sneutrino as the lightest supersymmetric particle (LSP). The discussion is carried out in the “[Formula: see text] from [Formula: see text]” supersymmetric standard model [Formula: see text], where the presence of [Formula: see text]-parity breaking couplings involving right-handed neutrinos solves the [Formula: see text] problem and reproduces neutrino data. The sneutrinos are pair produced via a virtual [Formula: see text], [Formula: see text] or [Formula: see text] in the [Formula: see text] channel. From the prompt decay of a pair of left sneutrinos LSPs of any family, a significant diphoton signal plus missing transverse energy (MET) from neutrinos can be present in the mass range 118–132 GeV, with 13 TeV center-of-mass energy and an integrated luminosity of 100 fb[Formula: see text]. In addition, in the case of a pair of tau left sneutrinos LSPs, given the large value of the tau Yukawa coupling diphoton plus leptons an...
In order to explain the results in Eq.(l) one needs to go to a theory beyond the standard model (... more In order to explain the results in Eq.(l) one needs to go to a theory beyond the standard model (SM). Supersymmetry(SUSY) is an interesting possibility for new physics at TeV scale. There have been several proposals in recent times which attempt to explain the experimental data on neutrinos in the context of minimal supersymmetric standard model (MSSM) with bilinear and trilinear R-parity violation [2-4]. Due to R-parity violation the lightest supepparticle (LSP) is unstable forthis class ofmodels. However MSSM possesses the so-called "p-pioblem" l5l. related to the bilineart et^ p A, H in the MSSM superpotential. One ofthe solutions to The experimental results on neutrinos provide evidence of non-zero neutrino masses and mixing aneles. In this work we examine in detail the neulrino mass patterns and mixing angles in an extension of the minimal supersymmetiic standard model with three gauge-singlet neutrinos and R-parity violarion. The Majorana maises for the gauge-singlet neutrinos as well as the usual p-term for the Higgs Superfields are generated atthe electroweak scale through the vacuum expectation values ofthe singlet 6 n"rt.inor. The resulting effective mass matrix for the three light neutrinos have contributions from the seesaw mechanism involving the singlet neutrinos as well as due to the mixing with the heaq neutralinos. We show that evin with flavour diagonal neutrino Yukawa couplings the global data on three-flavour neutrinos can be well accounted for in this scenario at the tree level. We further study the decays ofthe lightest neutralino in this model. The lightest neutralino can be the lightest supersymmetric particte pSf;. We focus on different cases where the Iightest neutralino is either a bino or a higgsino or a gauge-singlei neutrino. We study the important phenomenological differences between these cases and find"out th"at certain ratios ofdecay branching ratios ofthe lightest neutralino are correlated with eitherthe solarorthe atmospheric (and reactor) neutrino angle. Neutrino oscillation experiments have confirmed nonzero masses and mixing-angles for neutrinos. Various experiments suggest that the mixing pattem of the three light neutrinos is bilarge, that isto say there are two large mixing angles and one small mixing angle. The data can be explained very well with the following set of mass squared differences and mixing angles at 3o c.L. ul 7.05 x 1o 5ev2 < Lml, ! 8.34 x 1o 5ev2, 2.07 x 10-3ev2 S Al-3r1 5, 2.75 x 10-3ev2, 30.39" I drz <37.46', 36.87' 51zt < 54.94", d13 < 13.69", (1) where L.m!, = mf; ml.
New data on the lepton mixing angle θ_13 imply that the eμ element of the matrix m_ν m_ν^†, where... more New data on the lepton mixing angle θ_13 imply that the eμ element of the matrix m_ν m_ν^†, where m_ν is the neutrino Majorana mass matrix, cannot vanish. This implies a lower limit on lepton flavor violating processes in the eμ sector in a variety of frameworks, including Higgs triplet models or the concept of minimal flavor violation in the lepton sector. We illustrate this for the branching ratio of μ→ e γ in the type II seesaw mechanism, in which a Higgs triplet is responsible for neutrino mass and also mediates lepton flavor violation. We also discuss processes like μ→ ee̅e and μ→ e conversion in nuclei. Since these processes have sensitivity on the individual entries of m_ν, their rates can still be vanishingly small.
The "μ from ν" supersymmetric standard model (μνSSM) can accommodate the newly discover... more The "μ from ν" supersymmetric standard model (μνSSM) can accommodate the newly discovered Higgs-like scalar boson with a mass around 125 GeV. This model provides a solution to the μ-problem and simultaneously reproduces correct neutrino physics by the simple use of right-handed neutrino superfields. These new superfields together with the introduced R-parity violation can produce novel and characteristic signatures of the μνSSM at the LHC. We explore the signatures produced through two-body Higgs decays into the new states, provided that these states lie below in the mass spectrum. For example, a pair produced light neutralinos depending on the associated decay length can give rise to displaced multi-leptons/taus/jets/photons with small/moderate missing transverse energy. In the same spirit, a Higgs-like scalar decaying to a pair of scalars/pseudoscalars can produce final states with prompt multi-leptons/taus/jets/photons.
The ATLAS and CMS collaborations have recently released their new analyses of the diphoton search... more The ATLAS and CMS collaborations have recently released their new analyses of the diphoton searches. We look in detail the consequences of their results deriving strong constraints on models where a scalar resonance s decays into two light pseudoscalars which in turn decay into two pairs of collimated photons, mis-identified with two real photons. In our construction, all mass terms are generated dynamically, and only one pair of vector-like fermions generate couplings which will be probed using the upcoming LHC data. Moreover, we show that a stable dark matter candidate, respecting the cosmological constraints, is naturally affordable in the model.
In this work, we investigate the phenomenological consequences of a doubly charged scalar which m... more In this work, we investigate the phenomenological consequences of a doubly charged scalar which may belong to different uncoloured scalar multiplets. This doubly charged scalar couples to the charged leptons as well as gauge bosons, which we parametrize in a model independent way. Restricting ourselves in the regime of conserved charged-parity (CP), we assume only a few non-zero Yukawa couplings (y_μℓ, where ℓ=e,μ,τ) between the doubly charged scalar and the charged leptons. Our choices allow the doubly charged scalar to impinge low-energy processes like anomalous magnetic moment of muon and a few possible charged lepton flavour violating (CLFV) processes. These same Yukawa couplings are also instrumental in producing same-sign dilepton signatures at the LHC. In this article we examine the impact of individual contributions from the diagonal and off-diagonal Yukawa couplings in the light of muon (g-2) excess. Subsequently, we use the derived information to inquire the possible CLFV ...
We investigate signatures induced by a very light pseudoscalar Higgs in neutralino decays in the ... more We investigate signatures induced by a very light pseudoscalar Higgs in neutralino decays in the Next-to-Minimal Supersymmetric Standard Model (NMSSM) and determine their observability at the LHC. We concentrate on scenarios which feature two light scalar Higgs bosons (one of them is SM-like with a mass of 125 GeV and a singlet-like lighter one) with a very light (singlet-like) pseudoscalar Higgs in the mass range 2m_tau < m_a1 < 2m_b. We consider neutralino-chargino pair production and the subsequent decay X_2,3-> X_1 a1, which leads to topologies involving multi-leptons and missing transverse energy. We determine a set of selection cuts that can effectively isolate the signal from backgrounds of the Standard Model or the Minimal Supersymmetric Standard Model. We also exemplify the procedure with a set of benchmark points, for which we compute the expected number of events and signal strength for LHC with 8 TeV center of mass energy. We show that this signal can already be...
We investigate signatures of the minimal supersymmetric inverse seesaw model at the large hadron ... more We investigate signatures of the minimal supersymmetric inverse seesaw model at the large hadron collider (LHC) with three isolated leptons and large missing energy (3\ell + \mET or 2\ell + 1\tau + \mET, with \ell=e,\mu) in the final state. This signal has its origin in the decay of chargino-neutralino (\chpm1\ntrl2) pair, produced in pp collisions. The two body decays of the lighter chargino into a charged lepton and a singlet sneutrino has a characteristic decay pattern which is correlated with the observed large atmospheric neutrino mixing angle. This correlation is potentially observable at the LHC by looking at the ratios of cross sections of the trilepton + \mET channels in certain flavour specific modes. We show that even after considering possible leading standard model backgrounds these final states can lead to reasonable discovery significance at the LHC with both 7 TeV and 14 TeV center-of-mass energy.
In this article we propose a simultaneous collider search strategy for a pair of scalar bosons in... more In this article we propose a simultaneous collider search strategy for a pair of scalar bosons in the NMSSM through the decays of a very light pseudoscalar. The massive scalar has a mass around 126 GeV while the lighter one can have a mass in the vicinity of 98 GeV (thus explaining an apparent LEP excess) or be much lighter. The successive decay of this scalar pair into two light pseudoscalars, followed by leptonic pseudoscalar decays, produces clean multi-lepton final states with small or no missing energy. Furthermore, this analysis offers an alternate leptonic probe for the 126 GeV scalar that can be comparable with the ZZ* search channel. We emphasize that a dedicated experimental search for multi-lepton final states can be an useful probe for this scenario and, in general, for the NMSSM Higgs sector. We illustrate our analysis with two representative benchmark points and show how the LHC configuration with 8 TeV center-of-mass energy and 25 inverse femtobarns of integrated lumi...
Nonstandard on-shell decays of W^± and Z bosons are possible within the framework of extended sup... more Nonstandard on-shell decays of W^± and Z bosons are possible within the framework of extended supersymmetric models, i.e., with singlet states and/or new couplings compared to the minimal supersymmetric standard model. These modes are typically encountered in regions of the parameter space with light singlet-like scalars, pseudoscalars, and neutralinos. In this letter we emphasize how these states can lead to novel signals at colliders from Z- or W^±-boson decays with prompt or displaced multileptons/tau jets/jets/photons in the final states. These new modes would give distinct evidence of new physics even when direct searches remain unsuccessful. We discuss the possibilities of probing these new signals using the existing LHC run-I data set. We also address the same in the context of the LHC run-II, as well as for the future colliders. We exemplify our observations with the "μ from ν" supersymmetric standard model, where three generations of right-handed neutrino superfie...
Both the ATLAS and CMS collaborations have recently observed an excess in the di-photon invariant... more Both the ATLAS and CMS collaborations have recently observed an excess in the di-photon invariant mass distribution in the vicinity of 750 GeV with a local significance of 3 . In this article we try to investigate this excess in the context of a minimal simplified framework assuming e ective interactions of the hinted resonance with photons and gluons. We scrutinise the consistency of this observation with possible accompanying yet hitherto unseen signatures of this resonance. Subsequently, we try to probe the nature of new particles, e.g., spin, electric charge and number of colour, etc., that could remain instrumental to explain this excess through loop-mediation.
In this thesis we try to discuss certain phenomenological aspects of an R-parity violating non-mi... more In this thesis we try to discuss certain phenomenological aspects of an R-parity violating non-minimal supersymmetric model, called $\mu\nu$SSM. We show that $\mu\nu$SSM can provide a solution to the $\mu$-problem of supersymmetry and can simultaneously accommodate the existing three flavour global data from neutrino experiments even at the tree level with the simple choice of flavour diagonal neutrino Yukawa couplings. We show that it is also possible to achieve different mass hierarchies for light neutrinos at the tree level itself. In $\mu\nu$SSM, the effect of R-parity violation together with a seesaw mechanism with TeV scale right-handed neutrinos are instrumental for light neutrino mass generation. We also analyze the stability of tree level neutrino masses and mixing with the inclusion of one-loop radiative corrections. In addition, we investigate the sensitivity of the one-loop corrections to different light neutrino mass orderings. Decays of the lightest supersymmetric part...
We analyze relevant signals expected at the LHC for a left sneutrino as the lightest supersymmetr... more We analyze relevant signals expected at the LHC for a left sneutrino as the lightest supersymmetric particle (LSP). The discussion is carried out in the “[Formula: see text] from [Formula: see text]” supersymmetric standard model [Formula: see text], where the presence of [Formula: see text]-parity breaking couplings involving right-handed neutrinos solves the [Formula: see text] problem and reproduces neutrino data. The sneutrinos are pair produced via a virtual [Formula: see text], [Formula: see text] or [Formula: see text] in the [Formula: see text] channel. From the prompt decay of a pair of left sneutrinos LSPs of any family, a significant diphoton signal plus missing transverse energy (MET) from neutrinos can be present in the mass range 118–132 GeV, with 13 TeV center-of-mass energy and an integrated luminosity of 100 fb[Formula: see text]. In addition, in the case of a pair of tau left sneutrinos LSPs, given the large value of the tau Yukawa coupling diphoton plus leptons an...
New data on the lepton mixing angle $\theta_{13}$ imply that the $e\mu$ element of the matrix $m_... more New data on the lepton mixing angle $\theta_{13}$ imply that the $e\mu$ element of the matrix $m_\nu m_\nu^\dagger$, where $m_\nu$ is the neutrino Majorana mass matrix, cannot vanish. This implies a lower limit on lepton flavor violating processes in the $e\mu$ sector in a variety of frameworks, including Higgs triplet models or the concept of minimal flavor violation in the lepton sector. We illustrate this for the branching ratio of $\mu \to e \gamma$ in the type II seesaw mechanism, in which a Higgs triplet is responsible for neutrino mass and also mediates lepton flavor violation. We also discuss processes like $\mu\to e\bar{e}e$ and $\mu\to e$ conversion in nuclei. Since these processes have sensitivity on the individual entries of $m_\nu$, their rates can still be vanishingly small.
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