Choong Sun Kim - Academia.edu (original) (raw)
Papers by Choong Sun Kim
arXiv (Cornell University), Sep 19, 2022
Using the well established principles of Lorentz invariance, CP and CPT symmetry, and quantum sta... more Using the well established principles of Lorentz invariance, CP and CPT symmetry, and quantum statistics we do a model-independent study of effects of possible non-standard couplings of (Dirac and Majorana) neutrinos. The study is sensitive to the different quantum statistical properties of the Dirac and Majorana neutrinos which, contrary to neutrino-mediated processes of lepton number violation, could lead to observable effects not suppressed by the small ratios of neutrino and heavier particle masses. For processes with a neutrino-antineutrino pair of the same flavor in the final state, we formulate the "Dirac Majorana confusion theorem (DMCT)" showing why it is normally very difficult to observe the different behaviour of both kinds of neutrinos in experiments if they have only the standard model (SM)-like left-handed vector couplings to gauge bosons. We discuss deviations from the confusion theorem in the presence of nonstandard neutrino interactions, allowing to discover or constrain such novel couplings. We illustrate the general results with two chosen examples of neutral current processes, Z → ν ν and P i → P f ν ν (with P i, f denoting pseudoscalar mesons, such as B, K, π). Our analysis shows that using 3-body decays the presence of non-standard interactions can not only be constrained but one can also distinguish between Dirac and Majorana neutrino possibilities.
Journal of High Energy Physics, 2020
The disagreement between the standard model prediction and the experimental measurement of muon a... more The disagreement between the standard model prediction and the experimental measurement of muon anomalous magnetic moment can be alleviated by invoking an additional particle which is either a vector boson (X1) or a scalar (X0). This new particle, with the mass mX ≲ 2mμ, can be searched for in the decay J/ψ → μ−μ+X, where X is missing. Our numerical study shows that the search is quite feasible at the BESIII experiment in the parameter space allowed by muon g − 2 measurements.
Physical Review D, 2019
We analyze, in a fully model-independent manner, the effects of new physics on a few semi-hadroni... more We analyze, in a fully model-independent manner, the effects of new physics on a few semi-hadronic threebody meson decays of the type P i → P f f 1 f 2 , where P i , P f are well chosen pseudo-scalar mesons and f 1,2 denote fermions out of which at least one gets detected in experiments. We find that the angular distribution of events of these decays can probe many interesting new physics, such as the nature of the intermediate particle that can cause lepton-flavor violation, or presence of heavy sterile neutrino, or new intermediate particles, or new interactions. We also provide angular asymmetries which can quantify the effects of new physics in these decays. We illustrate the effectiveness of our proposed methodology with a few well chosen decay modes showing effects of certain new physics possibilities without any hadronic uncertainties.
Physics Letters B, 2015
We systematically analyze the radiative corrections to the S 3 symmetric neutrino mass matrix at ... more We systematically analyze the radiative corrections to the S 3 symmetric neutrino mass matrix at high energy scale, say the GUT scale, in the charged lepton basis. There are significant corrections to the neutrino parameters both in the Standard Model (SM) and Minimal Supersymmetric Standard Model (MSSM) with large tanβ, when the renormalization group evolution (RGE) and seesaw threshold effects are taken into consideration. We find that in the SM all three mixing angles and atmospheric mass squared difference are simultaneously obtained in their current 3σ ranges at the electroweak scale. However, the solar mass squared difference is found to be larger than its allowed 3σ range at the low scale in this case. There are significant contributions to neutrino masses and mixing angles in the MSSM with large tanβ from the RGEs even in the absence of seesaw threshold corrections. However, we find that the mass squared differences and the mixing angles are obtained in their current 3σ ranges at low energy when the seesaw threshold effects are also taken into account in the MSSM with large tanβ.
Physical Review D, 2017
Semileptonic b → c transitions, and in particular the ratios R(D (*)) = Γ(B→D (*) τ ν) Γ(B→D (*) ... more Semileptonic b → c transitions, and in particular the ratios R(D (*)) = Γ(B→D (*) τ ν) Γ(B→D (*) ν) , can be used to test the universality of the weak interactions. In light of the recent discrepancies between the experimental measurements of these observables by BaBar, Belle and LHCb and the Standard Model predicted values, we study the robustness of the latter. Our analysis reveals that R(D) might be enhanced by lepton mass effects associated to the mostly unknown scalar form factor. In constrast, the Standard Model prediction for R(D *) is found to be more robust, since possible pollutions from B * contributions turn out to be negligibly small, which indicates that R(D *) is a promising observable for searches of new physics.
Physics Letters B, 2009
We present a complete study of R-parity violating supersymmetric effects in thirteen exclusive an... more We present a complete study of R-parity violating supersymmetric effects in thirteen exclusive and inclusive semi-leptonic b → (s, d)νν decays, including B + u → K (*)+ νν, B 0 d → K (*)0 νν, B 0 s → φνν, B 0 d → π 0 (ρ 0)νν, B + u → π + (ρ +)νν, B 0 s → K (*)0 νν and B → X s,d νν decay modes, and we find those thirteen modes are very sensitive to the constrained R-parity violating couplings. We derive stringent bounds on relevant R-parity violating couplings, which are based on all existent experimental upper limits of involved semi-leptonic decays. In addition, we also investigate the sensitivities of the branching ratios and di-neutrino invariant mass spectra to the survived R-parity violating coupling spaces. Since the experimental bounds would become much better soon through SuperB , we expect that future experiments will greatly strengthen our bounds.
Physical Review D, 2014
A triplet dark matter candidate from thermal leptogenesis is considered with building a model. Th... more A triplet dark matter candidate from thermal leptogenesis is considered with building a model. The model is based on the standard two Higgs doublet model and seesaw mechanism with Higgs triplets. The parameters (couplings and masses) are adjusted for the observed small neutrino mass and the leptogenesis. Dark matter particles can annihilate and decay in this model. The time evolution of the dark matter number is governed by (co)annihilations in the expanding universe, and its mass is constrained by the observed relic density. The dark matter can decay into final states with three leptons (two charged leptons and one neutrino). We investigate whether the decay in the galaxy can account for cosmic ray anomalies in the positron and electron spectrum. A noticeable point is that if the dark matter decays into each lepton with different branching ratios, cosmic ray anomalies in AMS-02 measurements of the positron fraction and the Fermi LAT measurements of the electrons-plus-positrons flux could be simultaneously accounted for from its decay products. The leptogenesis within this model is studied in an appendix.
Physical Review D, 1996
We examine the magnetic eld dependence of the muonium(+ e)antimuonium(e +) conversion in the mode... more We examine the magnetic eld dependence of the muonium(+ e)antimuonium(e +) conversion in the models which accommodate the dilepton gauge bosons. The eective Hamiltonian for the conversion due to dileptons turns out to be in the (V A) (V + A) form and, in consequence, the conversion probability is rather insensitive to the strength of the magnetic eld. The reduction is less than 20% for up to B 300 G and 33% even in the large B limit.
Non-vanishing Ue3 has been theoretically related to a certain flavor symmetry breaking in the neu... more Non-vanishing Ue3 has been theoretically related to a certain flavor symmetry breaking in the neutrino sector. We propose a scenario to break the μ − τ symmetry so as to accommodate the non-vanishing Ue3. Our scenario is constructed in the context of a seesaw model, and the μ − τ symmetry breaking is achieved by introducing a CP phase in the Dirac Yukawa matrix. We also show how the deviation of θ23 from the maximal mixing and non-vanishing Ue3 depend on the CP phase. Neutrino mixings and the neutrino mass-squared differences are discussed, and the amplitude in neutrinoless double beta decay mee are also predicted. We found that a tiny breaking of the μ− τ symmetry due to mass splitting between two degenerate heavy Majorana neutrinos on top of the Dirac CP phase can lead to successful leptogenesis. We examine how leptogenesis can be related with low energy neutrino measurement, and show that our predictions for Ue3 and mee can be constrained by the current observation of baryon asym...
X iv :0 81 1. 14 58 v1 [ he pph ] 1 0 N ov 2 00 8 Bridges of Low Energy observables with Leptogen... more X iv :0 81 1. 14 58 v1 [ he pph ] 1 0 N ov 2 00 8 Bridges of Low Energy observables with Leptogenesis in μ− τ Reflection Symmetry Y. H. Ahn, Sin Kyu Kang, C. S. Kim, T. Phong Nguyen a Institute of Physics, Academia Sinica, Taipei, Taiwan 115, ROC b School of Liberal Arts, Seoul National Univ. of Technology, Seoul 139-743, Korea c Dept. of Physics and IPAP, Yonsei University, Seoul 120-749, Korea Abstract We consider an exact μ − τ reflection symmetry in neutrino sector realized at the GUT scale in the context of the seesaw model with and without supersymmetry. Assuming the two lighter heavy Majorana neutrinos are degenerate at the GUT scale, it is shown that the renormalization group (RG) evolution from the GUT scale to the seesaw scale gives rise to breaking of the μ − τ symmetry and a tiny splitting between two degenerate heavy Majorana neutrino masses as well as small variations of the CP phases in Yν , which are essential to achieve a successful leptogenesis. Such small RG effec...
International Journal of Modern Physics A, 2016
There is a growing interest for the search of new light gauge bosons. The small mass of a new bos... more There is a growing interest for the search of new light gauge bosons. The small mass of a new boson can turn various kinds of low-energy experiments to a new discovery machine, depending on their couplings to the Standard Model particles. It is important to understand the properties of each type of gauge boson and their current constraints for a given mass. While the dark photon (which couples to the electric charges) and the [Formula: see text] gauge boson have been well studied in an extensive mass range, the [Formula: see text] gauge boson has not been fully investigated yet. We consider the gauge boson of the [Formula: see text] in a wide mass range [Formula: see text] and investigate the constraints on its coupling from various experiments, discussing the similarities and differences from the dark photon and the [Formula: see text] gauge boson.
Journal of High Energy Physics, 2016
We evaluate the prompt atmospheric neutrino flux at high energies using three different framework... more We evaluate the prompt atmospheric neutrino flux at high energies using three different frameworks for calculating the heavy quark production cross section in QCD: NLO perturbative QCD, k T factorization including low-x resummation, and the dipole model including parton saturation. We use QCD parameters, the value for the charm quark mass and the range for the factorization and renormalization scales that provide the best description of the total charm cross section measured at fixed target experiments, at RHIC and at LHC. Using these parameters we calculate differential cross sections for charm and bottom production and compare with the latest data on forward charm meson production from LHCb at 7 TeV and at 13 TeV, finding good agreement with the data. In addition, we Open Access, c The Authors. Article funded by SCOAP 3 .
Physical Review D, 2012
In light of the recent neutrino experiment results from Daya Bay and RENO Collaborations, we stud... more In light of the recent neutrino experiment results from Daya Bay and RENO Collaborations, we study phenomenology of neutrino mixing angles in the Type III seesaw model with an discrete A 4 × Z 2 symmetry, whose spontaneously breaking scale is much higher than the electroweak scale. At tree level, the tri-bimaximal (TBM) form of the lepton mixing matrix can be obtained from leptonic Yukawa interactions in a natural way. We introduce all possible effective dimension-5 operators, invariant under the Standard Model gauge group and A 4 × Z 2 , and explicitly show that they induce a deviation of the lepton mixing from the TBM mixing matrix, which can explain a large mixing angle θ 13 together with small deviations of the solar and atmospheric mixing angles from the TBM. Two possible scenarios are investigated, by taking into account either negligible or sizable contributions from the light charged lepton sector to the lepton mixing matrix. Especially it is found in the latter scenario that all the neutrino experimental data, including the recent bestfit value of θ 13 = 8.68 • , can be accommodated. The leptonic CP violation characterized by the Jarlskog invariant J CP has a non-vanishing value, indicating a signal of maximal CP violation.
Physical Review D, 2015
We consider the SU (3) C ⊗SU (3) L ⊗U (1) X ⊗U (1) N (3-3-1-1) model at the GUT scale with implic... more We consider the SU (3) C ⊗SU (3) L ⊗U (1) X ⊗U (1) N (3-3-1-1) model at the GUT scale with implication for inflation and leptogenesis. The mass spectra of the neutral Higgs bosons and neutral gauge bosons are reconsidered when the scale of the 3-3-1-1 breaking is much larger than that of the ordinary SU (3) C ⊗ SU (3) L ⊗ U (1) X (3-3-1) breaking. We investigate how the 3-3-1-1 model generates an inflation by identifying the scalar field that spontaneously breaks the U (1) N symmetry to inflaton as well as including radiative corrections for the inflaton potential. We figure out the parameter spaces appeared in the inflaton potential that satisfy the conditions for an inflation model and obtain the inflaton mass an order of 10 13 GeV. The inflaton can dominantly decay into a pair of light Higgs bosons or a pair of heavy Majorana neutrinos which lead, respectively, to a reheating temperature of 10 9 GeV order appropriate to a thermal leptogenesis scenario or to a reduced reheating temperature corresponding to a non-thermal leptogenesis scenario. We calculate the lepton asymmetry which yields baryon asymmetry successfully for both the thermal and non-thermal cases.
We show that the economical 3-3-1 model has a dark mater candidate. It is a real scalar H_1^0 in ... more We show that the economical 3-3-1 model has a dark mater candidate. It is a real scalar H_1^0 in which main part is bilepton (with lepton number 2) and its mass is in the range of some TeVs. We calculate the relic abundance of H_1^0 dark matter by using micrOMEGAs 2.4 and figure out parameter space satisfying the WMAP constraints. Direct and indirect searches are studied for a special choice of parameters in the WMAP - allowed region.
Physics Letters B, 2007
We consider a variant of seesaw mechanism by introducing extra singlet neutrinos, with which we s... more We consider a variant of seesaw mechanism by introducing extra singlet neutrinos, with which we show how the low scale leptogenesis is realized without imposing the tiny mass splitting between two heavy Majorana neutrinos required in the resonant leptogenesis. Thus, we can avoid the socalled gravitino problem when our scenario is supersymmetrized. We show that an introduction of the new singlet fermion leads to a new contribution which can enhance the lepton asymmetry for certain range of parameter space. We also examine how both the light neutrino mass spectrum and relatively light sterile neutrinos of order a few 100 MeV can be achieved without being in conflict with the constraints on the mixing between the active and sterile neutrinos.
Physics Letters B, 2007
Motivated by the recent measurements of the Bs − Bs mass difference from the DØ and CDF collabora... more Motivated by the recent measurements of the Bs − Bs mass difference from the DØ and CDF collaborations, we probe new physics effects in the Bq − Bq mixing within the context of the supersymmetric grand unified model (SUSY GUT). We find that new physics effects in B s(d) − B s(d) mixing lead to the correlated information in the branching fractions of the lepton flavor violating decays, which may serve as a test of the SUSY GUT. We also discuss the implication of such new physics effects on the quark-lepton complementarity in the neutrino mixings.
![Research paper thumbnail of Erratum to “Doubly coexisting dark matter candidates in an extended seesaw model” [Phys. Lett. B 675 (2009) 203]](https://attachments.academia-assets.com/116603162/thumbnails/1.jpg)
](Physics Letters B, 2011
We examine how a scenario of coexisting two-particle dark mater can be realized in the extended s... more We examine how a scenario of coexisting two-particle dark mater can be realized in the extended seesaw model, which we have proposed previously to accommodate small neutrino masses and low scale leptogenesis with an introduction of singlet Majorana neutrino S and singlet scalar φ. We now impose the discrete symmetry Z 2 × Z ′ 2 and introduce new renormalizable interaction terms with a new heavy singlet scalar particle Φ so as for previously introduced S and φ to be doubly coexisting dark matter candidates. Depending on the mass spectrum of the two dark matter candidates, the annihilation process either SS −→ φφ or φφ −→ SS is of particular interest because the annihilation cross sections for the processes can be so large that the relic abundance of decaying particle should get lowered, which in turn makes the constraints on its parameter space relaxed, compared with the case of one and only one dark matter candidate. We discuss the implications of the dark matter detection through the scattering off the nucleus of the detecting material on our scenarios for dark matter candidates. We also study the implications for the search of invisible Higgs decay at LHC, which may serve as a probe of our scenario for dark matter.
arXiv (Cornell University), Sep 19, 2022
Using the well established principles of Lorentz invariance, CP and CPT symmetry, and quantum sta... more Using the well established principles of Lorentz invariance, CP and CPT symmetry, and quantum statistics we do a model-independent study of effects of possible non-standard couplings of (Dirac and Majorana) neutrinos. The study is sensitive to the different quantum statistical properties of the Dirac and Majorana neutrinos which, contrary to neutrino-mediated processes of lepton number violation, could lead to observable effects not suppressed by the small ratios of neutrino and heavier particle masses. For processes with a neutrino-antineutrino pair of the same flavor in the final state, we formulate the "Dirac Majorana confusion theorem (DMCT)" showing why it is normally very difficult to observe the different behaviour of both kinds of neutrinos in experiments if they have only the standard model (SM)-like left-handed vector couplings to gauge bosons. We discuss deviations from the confusion theorem in the presence of nonstandard neutrino interactions, allowing to discover or constrain such novel couplings. We illustrate the general results with two chosen examples of neutral current processes, Z → ν ν and P i → P f ν ν (with P i, f denoting pseudoscalar mesons, such as B, K, π). Our analysis shows that using 3-body decays the presence of non-standard interactions can not only be constrained but one can also distinguish between Dirac and Majorana neutrino possibilities.
Journal of High Energy Physics, 2020
The disagreement between the standard model prediction and the experimental measurement of muon a... more The disagreement between the standard model prediction and the experimental measurement of muon anomalous magnetic moment can be alleviated by invoking an additional particle which is either a vector boson (X1) or a scalar (X0). This new particle, with the mass mX ≲ 2mμ, can be searched for in the decay J/ψ → μ−μ+X, where X is missing. Our numerical study shows that the search is quite feasible at the BESIII experiment in the parameter space allowed by muon g − 2 measurements.
Physical Review D, 2019
We analyze, in a fully model-independent manner, the effects of new physics on a few semi-hadroni... more We analyze, in a fully model-independent manner, the effects of new physics on a few semi-hadronic threebody meson decays of the type P i → P f f 1 f 2 , where P i , P f are well chosen pseudo-scalar mesons and f 1,2 denote fermions out of which at least one gets detected in experiments. We find that the angular distribution of events of these decays can probe many interesting new physics, such as the nature of the intermediate particle that can cause lepton-flavor violation, or presence of heavy sterile neutrino, or new intermediate particles, or new interactions. We also provide angular asymmetries which can quantify the effects of new physics in these decays. We illustrate the effectiveness of our proposed methodology with a few well chosen decay modes showing effects of certain new physics possibilities without any hadronic uncertainties.
Physics Letters B, 2015
We systematically analyze the radiative corrections to the S 3 symmetric neutrino mass matrix at ... more We systematically analyze the radiative corrections to the S 3 symmetric neutrino mass matrix at high energy scale, say the GUT scale, in the charged lepton basis. There are significant corrections to the neutrino parameters both in the Standard Model (SM) and Minimal Supersymmetric Standard Model (MSSM) with large tanβ, when the renormalization group evolution (RGE) and seesaw threshold effects are taken into consideration. We find that in the SM all three mixing angles and atmospheric mass squared difference are simultaneously obtained in their current 3σ ranges at the electroweak scale. However, the solar mass squared difference is found to be larger than its allowed 3σ range at the low scale in this case. There are significant contributions to neutrino masses and mixing angles in the MSSM with large tanβ from the RGEs even in the absence of seesaw threshold corrections. However, we find that the mass squared differences and the mixing angles are obtained in their current 3σ ranges at low energy when the seesaw threshold effects are also taken into account in the MSSM with large tanβ.
Physical Review D, 2017
Semileptonic b → c transitions, and in particular the ratios R(D (*)) = Γ(B→D (*) τ ν) Γ(B→D (*) ... more Semileptonic b → c transitions, and in particular the ratios R(D (*)) = Γ(B→D (*) τ ν) Γ(B→D (*) ν) , can be used to test the universality of the weak interactions. In light of the recent discrepancies between the experimental measurements of these observables by BaBar, Belle and LHCb and the Standard Model predicted values, we study the robustness of the latter. Our analysis reveals that R(D) might be enhanced by lepton mass effects associated to the mostly unknown scalar form factor. In constrast, the Standard Model prediction for R(D *) is found to be more robust, since possible pollutions from B * contributions turn out to be negligibly small, which indicates that R(D *) is a promising observable for searches of new physics.
Physics Letters B, 2009
We present a complete study of R-parity violating supersymmetric effects in thirteen exclusive an... more We present a complete study of R-parity violating supersymmetric effects in thirteen exclusive and inclusive semi-leptonic b → (s, d)νν decays, including B + u → K (*)+ νν, B 0 d → K (*)0 νν, B 0 s → φνν, B 0 d → π 0 (ρ 0)νν, B + u → π + (ρ +)νν, B 0 s → K (*)0 νν and B → X s,d νν decay modes, and we find those thirteen modes are very sensitive to the constrained R-parity violating couplings. We derive stringent bounds on relevant R-parity violating couplings, which are based on all existent experimental upper limits of involved semi-leptonic decays. In addition, we also investigate the sensitivities of the branching ratios and di-neutrino invariant mass spectra to the survived R-parity violating coupling spaces. Since the experimental bounds would become much better soon through SuperB , we expect that future experiments will greatly strengthen our bounds.
Physical Review D, 2014
A triplet dark matter candidate from thermal leptogenesis is considered with building a model. Th... more A triplet dark matter candidate from thermal leptogenesis is considered with building a model. The model is based on the standard two Higgs doublet model and seesaw mechanism with Higgs triplets. The parameters (couplings and masses) are adjusted for the observed small neutrino mass and the leptogenesis. Dark matter particles can annihilate and decay in this model. The time evolution of the dark matter number is governed by (co)annihilations in the expanding universe, and its mass is constrained by the observed relic density. The dark matter can decay into final states with three leptons (two charged leptons and one neutrino). We investigate whether the decay in the galaxy can account for cosmic ray anomalies in the positron and electron spectrum. A noticeable point is that if the dark matter decays into each lepton with different branching ratios, cosmic ray anomalies in AMS-02 measurements of the positron fraction and the Fermi LAT measurements of the electrons-plus-positrons flux could be simultaneously accounted for from its decay products. The leptogenesis within this model is studied in an appendix.
Physical Review D, 1996
We examine the magnetic eld dependence of the muonium(+ e)antimuonium(e +) conversion in the mode... more We examine the magnetic eld dependence of the muonium(+ e)antimuonium(e +) conversion in the models which accommodate the dilepton gauge bosons. The eective Hamiltonian for the conversion due to dileptons turns out to be in the (V A) (V + A) form and, in consequence, the conversion probability is rather insensitive to the strength of the magnetic eld. The reduction is less than 20% for up to B 300 G and 33% even in the large B limit.
Non-vanishing Ue3 has been theoretically related to a certain flavor symmetry breaking in the neu... more Non-vanishing Ue3 has been theoretically related to a certain flavor symmetry breaking in the neutrino sector. We propose a scenario to break the μ − τ symmetry so as to accommodate the non-vanishing Ue3. Our scenario is constructed in the context of a seesaw model, and the μ − τ symmetry breaking is achieved by introducing a CP phase in the Dirac Yukawa matrix. We also show how the deviation of θ23 from the maximal mixing and non-vanishing Ue3 depend on the CP phase. Neutrino mixings and the neutrino mass-squared differences are discussed, and the amplitude in neutrinoless double beta decay mee are also predicted. We found that a tiny breaking of the μ− τ symmetry due to mass splitting between two degenerate heavy Majorana neutrinos on top of the Dirac CP phase can lead to successful leptogenesis. We examine how leptogenesis can be related with low energy neutrino measurement, and show that our predictions for Ue3 and mee can be constrained by the current observation of baryon asym...
X iv :0 81 1. 14 58 v1 [ he pph ] 1 0 N ov 2 00 8 Bridges of Low Energy observables with Leptogen... more X iv :0 81 1. 14 58 v1 [ he pph ] 1 0 N ov 2 00 8 Bridges of Low Energy observables with Leptogenesis in μ− τ Reflection Symmetry Y. H. Ahn, Sin Kyu Kang, C. S. Kim, T. Phong Nguyen a Institute of Physics, Academia Sinica, Taipei, Taiwan 115, ROC b School of Liberal Arts, Seoul National Univ. of Technology, Seoul 139-743, Korea c Dept. of Physics and IPAP, Yonsei University, Seoul 120-749, Korea Abstract We consider an exact μ − τ reflection symmetry in neutrino sector realized at the GUT scale in the context of the seesaw model with and without supersymmetry. Assuming the two lighter heavy Majorana neutrinos are degenerate at the GUT scale, it is shown that the renormalization group (RG) evolution from the GUT scale to the seesaw scale gives rise to breaking of the μ − τ symmetry and a tiny splitting between two degenerate heavy Majorana neutrino masses as well as small variations of the CP phases in Yν , which are essential to achieve a successful leptogenesis. Such small RG effec...
International Journal of Modern Physics A, 2016
There is a growing interest for the search of new light gauge bosons. The small mass of a new bos... more There is a growing interest for the search of new light gauge bosons. The small mass of a new boson can turn various kinds of low-energy experiments to a new discovery machine, depending on their couplings to the Standard Model particles. It is important to understand the properties of each type of gauge boson and their current constraints for a given mass. While the dark photon (which couples to the electric charges) and the [Formula: see text] gauge boson have been well studied in an extensive mass range, the [Formula: see text] gauge boson has not been fully investigated yet. We consider the gauge boson of the [Formula: see text] in a wide mass range [Formula: see text] and investigate the constraints on its coupling from various experiments, discussing the similarities and differences from the dark photon and the [Formula: see text] gauge boson.
Journal of High Energy Physics, 2016
We evaluate the prompt atmospheric neutrino flux at high energies using three different framework... more We evaluate the prompt atmospheric neutrino flux at high energies using three different frameworks for calculating the heavy quark production cross section in QCD: NLO perturbative QCD, k T factorization including low-x resummation, and the dipole model including parton saturation. We use QCD parameters, the value for the charm quark mass and the range for the factorization and renormalization scales that provide the best description of the total charm cross section measured at fixed target experiments, at RHIC and at LHC. Using these parameters we calculate differential cross sections for charm and bottom production and compare with the latest data on forward charm meson production from LHCb at 7 TeV and at 13 TeV, finding good agreement with the data. In addition, we Open Access, c The Authors. Article funded by SCOAP 3 .
Physical Review D, 2012
In light of the recent neutrino experiment results from Daya Bay and RENO Collaborations, we stud... more In light of the recent neutrino experiment results from Daya Bay and RENO Collaborations, we study phenomenology of neutrino mixing angles in the Type III seesaw model with an discrete A 4 × Z 2 symmetry, whose spontaneously breaking scale is much higher than the electroweak scale. At tree level, the tri-bimaximal (TBM) form of the lepton mixing matrix can be obtained from leptonic Yukawa interactions in a natural way. We introduce all possible effective dimension-5 operators, invariant under the Standard Model gauge group and A 4 × Z 2 , and explicitly show that they induce a deviation of the lepton mixing from the TBM mixing matrix, which can explain a large mixing angle θ 13 together with small deviations of the solar and atmospheric mixing angles from the TBM. Two possible scenarios are investigated, by taking into account either negligible or sizable contributions from the light charged lepton sector to the lepton mixing matrix. Especially it is found in the latter scenario that all the neutrino experimental data, including the recent bestfit value of θ 13 = 8.68 • , can be accommodated. The leptonic CP violation characterized by the Jarlskog invariant J CP has a non-vanishing value, indicating a signal of maximal CP violation.
Physical Review D, 2015
We consider the SU (3) C ⊗SU (3) L ⊗U (1) X ⊗U (1) N (3-3-1-1) model at the GUT scale with implic... more We consider the SU (3) C ⊗SU (3) L ⊗U (1) X ⊗U (1) N (3-3-1-1) model at the GUT scale with implication for inflation and leptogenesis. The mass spectra of the neutral Higgs bosons and neutral gauge bosons are reconsidered when the scale of the 3-3-1-1 breaking is much larger than that of the ordinary SU (3) C ⊗ SU (3) L ⊗ U (1) X (3-3-1) breaking. We investigate how the 3-3-1-1 model generates an inflation by identifying the scalar field that spontaneously breaks the U (1) N symmetry to inflaton as well as including radiative corrections for the inflaton potential. We figure out the parameter spaces appeared in the inflaton potential that satisfy the conditions for an inflation model and obtain the inflaton mass an order of 10 13 GeV. The inflaton can dominantly decay into a pair of light Higgs bosons or a pair of heavy Majorana neutrinos which lead, respectively, to a reheating temperature of 10 9 GeV order appropriate to a thermal leptogenesis scenario or to a reduced reheating temperature corresponding to a non-thermal leptogenesis scenario. We calculate the lepton asymmetry which yields baryon asymmetry successfully for both the thermal and non-thermal cases.
We show that the economical 3-3-1 model has a dark mater candidate. It is a real scalar H_1^0 in ... more We show that the economical 3-3-1 model has a dark mater candidate. It is a real scalar H_1^0 in which main part is bilepton (with lepton number 2) and its mass is in the range of some TeVs. We calculate the relic abundance of H_1^0 dark matter by using micrOMEGAs 2.4 and figure out parameter space satisfying the WMAP constraints. Direct and indirect searches are studied for a special choice of parameters in the WMAP - allowed region.
Physics Letters B, 2007
We consider a variant of seesaw mechanism by introducing extra singlet neutrinos, with which we s... more We consider a variant of seesaw mechanism by introducing extra singlet neutrinos, with which we show how the low scale leptogenesis is realized without imposing the tiny mass splitting between two heavy Majorana neutrinos required in the resonant leptogenesis. Thus, we can avoid the socalled gravitino problem when our scenario is supersymmetrized. We show that an introduction of the new singlet fermion leads to a new contribution which can enhance the lepton asymmetry for certain range of parameter space. We also examine how both the light neutrino mass spectrum and relatively light sterile neutrinos of order a few 100 MeV can be achieved without being in conflict with the constraints on the mixing between the active and sterile neutrinos.
Physics Letters B, 2007
Motivated by the recent measurements of the Bs − Bs mass difference from the DØ and CDF collabora... more Motivated by the recent measurements of the Bs − Bs mass difference from the DØ and CDF collaborations, we probe new physics effects in the Bq − Bq mixing within the context of the supersymmetric grand unified model (SUSY GUT). We find that new physics effects in B s(d) − B s(d) mixing lead to the correlated information in the branching fractions of the lepton flavor violating decays, which may serve as a test of the SUSY GUT. We also discuss the implication of such new physics effects on the quark-lepton complementarity in the neutrino mixings.
Physics Letters B, 2011
We examine how a scenario of coexisting two-particle dark mater can be realized in the extended s... more We examine how a scenario of coexisting two-particle dark mater can be realized in the extended seesaw model, which we have proposed previously to accommodate small neutrino masses and low scale leptogenesis with an introduction of singlet Majorana neutrino S and singlet scalar φ. We now impose the discrete symmetry Z 2 × Z ′ 2 and introduce new renormalizable interaction terms with a new heavy singlet scalar particle Φ so as for previously introduced S and φ to be doubly coexisting dark matter candidates. Depending on the mass spectrum of the two dark matter candidates, the annihilation process either SS −→ φφ or φφ −→ SS is of particular interest because the annihilation cross sections for the processes can be so large that the relic abundance of decaying particle should get lowered, which in turn makes the constraints on its parameter space relaxed, compared with the case of one and only one dark matter candidate. We discuss the implications of the dark matter detection through the scattering off the nucleus of the detecting material on our scenarios for dark matter candidates. We also study the implications for the search of invisible Higgs decay at LHC, which may serve as a probe of our scenario for dark matter.