We study the Bc meson rare decay in order to search for the Majorana neutrino signal. It is found that the corresponding decay rate is sensitive to the Majorana neutrino mass and mixing angles. The signal of B~ --~ li...We study the Bc meson rare decay in order to search for the Majorana neutrino signal. It is found that the corresponding decay rate is sensitive to the Majorana neutrino mass and mixing angles. The signal of B~ --~ lil l~ Mm induced by the Majorana neutrino within the mass region mr 〈 mn 〈mB may be observed at LHCb.展开更多
We study one possible production mechanism for the hidden-charm pentaquark via a color-octet cc pair fragmentation in e^(+)e^(-)collision.The pentaquark production at B factory energy is dominated by e^(+)e^(-)→ccg→...We study one possible production mechanism for the hidden-charm pentaquark via a color-octet cc pair fragmentation in e^(+)e^(-)collision.The pentaquark production at B factory energy is dominated by e^(+)e^(-)→ccg→P_(c)+X,while at Z^(0)pole energy,there are several partonic processes playing significant role.Our results show that it is possible to search for the direct pentaquark production signal at e^(+)e^(-)colliders,which is important to understand the properties of pentaquark.展开更多
Precise determination of the Higgs boson self-couplings is essential for understanding the mechanism underlying electroweak symmetry breaking.However,owing to the limited number of Higgs boson pair events at the LHC,o...Precise determination of the Higgs boson self-couplings is essential for understanding the mechanism underlying electroweak symmetry breaking.However,owing to the limited number of Higgs boson pair events at the LHC,only loose constraints have been established to date.Current constraints are based on the assumption that the cross section is a quadratic function of the trilinear Higgs self-coupling within the framework.Incorporating higher-order quantum corrections from virtual Higgs bosons would significantly alter this functional form,introducing new quartic and cubic power dependencies on the trilinear Higgs self-coupling.To derive this new functional form,we propose a specialized renormalization procedure that tracks all Higgs self-couplings at each calculation step.Additionally,we introduce renormalization constants for coupling modifiers within the framework to ensure the cancellation of all ultraviolet divergences.With new functional forms of the cross sections in both the gluon-gluon fusion and vector boson fusion channels,the upper limit of kλ_(3H)=λ_(3H)^(SM)set by the ATLAS(CMS)collaboration is reduced from 6.6(6.49)to 5.4(5.37).However,extracting a meaningful constraint on the quartic Higgs self-coupling from Higgs boson pair production data remains challenging.We also present the invariant mass distributions of the Higgs boson pair at different values of the self-couplings,which could assist in setting optimal cuts for experimental analysis.展开更多
We discuss the landscape of flavor physics at the Circular Electron-Positron Collider(CEPC),based on the nominal luminosity outlined in its Technical Design Report.The CEPC is designed to operate in multiple modes to ...We discuss the landscape of flavor physics at the Circular Electron-Positron Collider(CEPC),based on the nominal luminosity outlined in its Technical Design Report.The CEPC is designed to operate in multiple modes to address a variety of tasks.At the Z pole,the expected production of 4 Tera Z bosons will provide unique and highly precise measurements of Z boson couplings,while the substantial number of boosted heavy-flavored quarks and leptons produced in clean Z decays will facilitate investigations into their flavor physics with unprecedented precision.We investigate the prospects of measuring various physics benchmarks and discuss their implications for particle theories and phenomenological models.Our studies indicate that,with its highlighted advantages and anticipated excellent detector performance,the CEPC can explore beauty andτphysics in ways that are superior to or complementary with the Belle II and Large-Hadron-Collider-beauty experiments,potentially enabling the detection of new physics at energy scales of 10 TeV and above.This potential also extends to the observation of yet-to-be-discovered rare and exotic processes,as well as testing fundamental principles such as lepton flavor universality,lepton and baryon number conservation,etc.,making the CEPC a vibrant platform for flavor physics research.The WW threshold scan,Higgs-factory operation and top-pair productions of the CEPC further enhance its merits in this regard,especially for measuring the Cabibbo-Kobayashi-Maskawa matrix elements,and Flavor-Changing-NeutralCurrent physics of Higgs boson and top quarks.We outline the requirements for detector performance and considerations for future development to achieve the anticipated scientific goals.The role of machine learning for innovative detector design and advanced reconstruction algorithms is also stressed.The CEPC flavor physics program not only develops new capabilities for exploring flavor physics beyond existing projects but also enriches the physics opportunities of this machine.It should be remarked that,given the richness of the CEPC flavor physics,this manuscript is not meant to be a comprehensive survey,but rather an investigation of representative cases.Uncovering the full potential of flavor physics at the CEPC will require further dedicated explorations in the future.展开更多
In the framework of the canonical seesaw model,we present a simple but viable scenario to explicitly break an S3L×S3R flavor symmetry in the leptonic sector.It turns out that the leptonic flavor mixing matrix is ...In the framework of the canonical seesaw model,we present a simple but viable scenario to explicitly break an S3L×S3R flavor symmetry in the leptonic sector.It turns out that the leptonic flavor mixing matrix is completely determined by the mass ratios of the charged leptons（i.e.,me/mμand mμ/mτ） and those of light neutrinos（i.e.,m1/m2 and m2/m3）.The latest global-fit results of the three neutrino mixing angles {θ12,θ13,θ23}and two neutrino mass-squared differences {？m212,？m312} at the 3σ level are used to constrain the parameter space of {m1/m2,m2/m3}.The predictions for the mass spectrum and flavor mixing are highlighted：（1） the neutrino mass spectrum shows a hierarchical pattern and a normal ordering,e.g.,m1≈2.2meV,m2≈8.8 meV and m3≈52.7 meV;（2） only the first octant of θ23 is allowed,namely,41.8？ θ23 43.3？;（3） the Dirac C P-violating phase δ ≈-22？deviates significantly from the maximal value-90？.All these predictions are ready to be tested in ongoing and forthcoming neutrino oscillation experiments.Moreover,we demonstrate that the cosmological matter-antimatter asymmetry can be explained via resonant leptogenesis,including the individual lepton-flavor effects.In our scenario,leptonic C P violation at low-and high-energy scales is closely connected.展开更多
The non-relativistic wave function framework is applied to study the production and decay of exotic hadrons, which can be effectively described as bound states of other hadrons. Employing the factorized formulation,wi...The non-relativistic wave function framework is applied to study the production and decay of exotic hadrons, which can be effectively described as bound states of other hadrons. Employing the factorized formulation,with the help of event generators, we investigate the production of exotic hadrons in multiproduction processes at high energy hadron colliders. This study provides crucial information for the measurements of the relevant exotic hadrons.展开更多
Lepton number violation processes can be induced by the Majorana neutrino exchange, which provide evidence for the Majorana nature of neutrinos. In addition to the natural explanation of the small neutrino masses,Type...Lepton number violation processes can be induced by the Majorana neutrino exchange, which provide evidence for the Majorana nature of neutrinos. In addition to the natural explanation of the small neutrino masses,Type-I seesaw mechanism predicts the existence of Majorana neutrinos. The aim of this work is to study the B meson rare decays B^+→K^((*))+μ^+μ^-in the Standard Model and its extensions, and then to investigate the same-sign decay process B^+→K^((*)-)μ^+μ^+. The corresponding dilepton invariant mass distributions are calculated. It is found that the dilepton angular distributions could shed light on the properties of new interactions induced by Majorana neutrinos.展开更多
We calculate the masses of the QQqq(Q=c,b:q=u,d,s)tetraquark states with the aid of heavy diquark-antiquark symmetry(HDAS)and the chromomagnetic interaction(CMI)model.The masses of the highestspin(J=2)tetraquarks that...We calculate the masses of the QQqq(Q=c,b:q=u,d,s)tetraquark states with the aid of heavy diquark-antiquark symmetry(HDAS)and the chromomagnetic interaction(CMI)model.The masses of the highestspin(J=2)tetraquarks that have only the(QQ)(3):(qq)_(3).color structure are related with those of conventional hadrons using HDAS.Thereafter,the masses of their partner states are determined with the mass splittings in the CMI model.Our numerical results reveal that(i)the lightest ccnn(n=u,d)is an I(J^(P))=0(1^(+))state around 3929 MeV(53 MeV above the DD^(*) threshold),and none of the double-charm tetraquarks are stable;(ii)the stable double-bottom tetraquarks are the lowest 0(1^(+))bbin around 10488 MeV(≈116 MeV below the BB^(*)threshold)and the lowest 1/2(1^(+))bbns around 10671 MeV(≈20 MeV below the BB_(s)^(*)/B_(s)B^(*)threshold);and(iii)the two lowest bcnn tetraquarks,namely the lowest 0(0^(+))around 7167 MeV and the lowest 0(1)around 7223 MeV,are in the nearthreshold states.Moreover,we discuss the constraints on the masses of double-heavy hadrons.Specifically,for the lowest nonstrange tetraquarks,we obtain T_(cc)<3965 MeV,T_(bb)<10627 MeV,and T_(bc)<7199 MeV.展开更多
We studied the spectrum and rearrangement decays of S-wave cs■tetraquark states in a simplified quark model.The masses and widths were estimated by assuming that X(4140)is the lower 1^(++)cs■tetraquark.Comparing our...We studied the spectrum and rearrangement decays of S-wave cs■tetraquark states in a simplified quark model.The masses and widths were estimated by assuming that X(4140)is the lower 1^(++)cs■tetraquark.Comparing our results with experimental measurements,we found that X(3960),recently observed by LHCb,can be considered the lowest 0^(++)sc■tetraquark state and X0(4140)could be the second lowest 0^(++)cs■tetraquark.Predictions of ratios between partial widths for the involved tetraquarks are provided in this paper.We aim to identify more cs■tetraquarks with J^(PC)=1^(+-),0^(++),and 2^(++).展开更多
A nonzero neutrino mass may be a sign of new physics beyond the standard model(SM).To explain the small neutrino mass,we can extend the SM using right-handed Majorana neutrinos in a low-scale seesaw mechanism,and the ...A nonzero neutrino mass may be a sign of new physics beyond the standard model(SM).To explain the small neutrino mass,we can extend the SM using right-handed Majorana neutrinos in a low-scale seesaw mechanism,and the CP violation effect can be induced due to the CP phase in the interference of heavy Majorana neutrinos.The existence of heavy Majorana neutrinos may lead to lepton number violation processes,which can be used to search for the signals of heavy Majorana neutrinos.In this paper,we focus on the CP violation effect related to two generations of heavy Majorana neutrinos at 15 GeV<m_(N1)<70 GeV in the pair production of W bosons and rare decays.It is valuable to investigate Majorana neutrino production signals and the related CP violation effects in rare W boson decays at future lepton colliders.展开更多
Heavy Majorana neutrinos beyond the standard model can simultaneously explain the origin of tiny neutRino masses and matter-antimatter asymmetry in our Universe.The existence of heavy Majorana neutrinos will also lead...Heavy Majorana neutrinos beyond the standard model can simultaneously explain the origin of tiny neutRino masses and matter-antimatter asymmetry in our Universe.The existence of heavy Majorana neutrinos will also lead to lepton number violation and confirm the possibility of rare lepton-number-violating W decays.With contributions from two different Majorana neutrinos,nonzero CP asymmetry may be generated from the rate difference between W decay and its CP-conjugate process.The aim of this study is to investigate the prospects of measuring CP violation in rare w decays via Majorana neutRInos at the LHC.Our calculations show that the induced CP asymmetry is independent of the Majorana neutrino mass for 15<m_(N)<70GeV.Such a CP asymmetry,if observed,would in turn provide unambiguous evidence of new physics beyond the standard model.展开更多
The finite mass of the heavy quark suppresses the collimated radiations;this is generally referred to as the dead cone effect.In this paper,we study the distribution of hadron multiplicity over the hadron opening angl...The finite mass of the heavy quark suppresses the collimated radiations;this is generally referred to as the dead cone effect.In this paper,we study the distribution of hadron multiplicity over the hadron opening angle with respect to the jet axis for various jet flavors.The corresponding measurement can be the most straightforward and simplest approach to explore the dynamical evolution of the radiations in the corresponding jet,which can expose the mass effect.We also propose a transverse energy-weighted angular distribution,which sheds light on the interplay between perturbative and non-perturbative effects in the radiation.Through Monte-Carlo simulations,our calculations show that the dead cone effect can be clearly observed by finding the ratio between the b and light-quark(inclusive)jets;this is expected to be measured at the LHC in the future.展开更多
Dark sector may couple to the Standard Model via one or more mediator particles.We discuss two types of mediators:the dark photon A’ and the dark scalar mediator Φ .The total cross-sections and various differential ...Dark sector may couple to the Standard Model via one or more mediator particles.We discuss two types of mediators:the dark photon A’ and the dark scalar mediator Φ .The total cross-sections and various differential distributions of the processes e+e-→qqA’ and e+e→qqφ（q=u,d,c,s and b quarks） are discussed.We focus on the study of the invisible due to the cleaner background at future e+e-colliders.It is found that the kinematic distributions of the two-jet system could be used to identify（or exclude） the dark photon and the dark scalar mediator,as well as to distinguish between them.We further study the possibility of a search for dark photons at a future CEPC experiment with s1/2=91.2 GeV and 240 GeV.With CEPC running at s1/2=91.2 GeV,it would be possible to perform a decisive measurement of the dark photon（20 GeV <mA’ <60 GeV） in less than one operating year.The lower limits of the integrated luminosity for the significance S/B1/2=2σ,3σ and 5σ are presented.展开更多
基金Supported by the National Science Foundation of China under Grant No.11275114China Postdoctoral Science Foundation under Grant No.2012T50604Natural Science Foundation of Shandong Province under Grant No.ZR2011AQ013
文摘We study the Bc meson rare decay in order to search for the Majorana neutrino signal. It is found that the corresponding decay rate is sensitive to the Majorana neutrino mass and mixing angles. The signal of B~ --~ lil l~ Mm induced by the Majorana neutrino within the mass region mr 〈 mn 〈mB may be observed at LHCb.
基金Supported by National Natural Science Foundation of China under Grant Nos.11775130,11775132,11635009,11325525the Natural Science Foundation of Shandong Province under Grant No.ZR2017MA002
文摘We study one possible production mechanism for the hidden-charm pentaquark via a color-octet cc pair fragmentation in e^(+)e^(-)collision.The pentaquark production at B factory energy is dominated by e^(+)e^(-)→ccg→P_(c)+X,while at Z^(0)pole energy,there are several partonic processes playing significant role.Our results show that it is possible to search for the direct pentaquark production signal at e^(+)e^(-)colliders,which is important to understand the properties of pentaquark.
基金Supported in part by the National Natural Science Foundation of China(12275156,12321005,12375076)and the Taishan Scholar Foundation of Shandong province(tsqn201909011)。
文摘Precise determination of the Higgs boson self-couplings is essential for understanding the mechanism underlying electroweak symmetry breaking.However,owing to the limited number of Higgs boson pair events at the LHC,only loose constraints have been established to date.Current constraints are based on the assumption that the cross section is a quadratic function of the trilinear Higgs self-coupling within the framework.Incorporating higher-order quantum corrections from virtual Higgs bosons would significantly alter this functional form,introducing new quartic and cubic power dependencies on the trilinear Higgs self-coupling.To derive this new functional form,we propose a specialized renormalization procedure that tracks all Higgs self-couplings at each calculation step.Additionally,we introduce renormalization constants for coupling modifiers within the framework to ensure the cancellation of all ultraviolet divergences.With new functional forms of the cross sections in both the gluon-gluon fusion and vector boson fusion channels,the upper limit of kλ_(3H)=λ_(3H)^(SM)set by the ATLAS(CMS)collaboration is reduced from 6.6(6.49)to 5.4(5.37).However,extracting a meaningful constraint on the quartic Higgs self-coupling from Higgs boson pair production data remains challenging.We also present the invariant mass distributions of the Higgs boson pair at different values of the self-couplings,which could assist in setting optimal cuts for experimental analysis.
基金financial support from the National Natural Science Foundation of China(NSFC)(12125507,12047503,12035008,2211530479,12475094,12135006,12075097,12375086,2022YFA1601903,12061141007,12375091,12342502,12235018,12335003,12105100,12475106,11961141015,12188102,12175245,12205171,12321005,tsqn202312052,2024HWYQ-005,12405121,12447167,12061141006,12405102,12125503,12305115,12075213,12335005,12235008)the Chinese Academy of Sciences(YSBR-101,XDB34030000)+11 种基金the National Key R&D Program of China(2022YFE0116900,2023YFA1606703,2022YFA1601901)the National Key Research and Development Program of China(2023YFA1606300)the Excellent Postdoctoral Program of Jiangsu Province(2023ZB891)the Shenzhen Science and Technology Program(202206193000001,20220816094256002)the Natural Science Foundation for Distinguished Young Scholars of Henan Province(242300421046)the Beijing Municipal Natural Science Foundation(JQ22002)the Area of Excellence(AoE/P-404/18-3)the General Research Fund(16304321)(both grants are issued by the Research Grants Council of Hong Kong S.A.R)the MOST National Key R&D Program(2023YFA1606303)the Shanghai Key Laboratory for Particle Physics and CosmologyKey Laboratory for Particle Astrophysics and Cosmology(Ministry of Education)Shanghai Jiao Tong University。
文摘We discuss the landscape of flavor physics at the Circular Electron-Positron Collider(CEPC),based on the nominal luminosity outlined in its Technical Design Report.The CEPC is designed to operate in multiple modes to address a variety of tasks.At the Z pole,the expected production of 4 Tera Z bosons will provide unique and highly precise measurements of Z boson couplings,while the substantial number of boosted heavy-flavored quarks and leptons produced in clean Z decays will facilitate investigations into their flavor physics with unprecedented precision.We investigate the prospects of measuring various physics benchmarks and discuss their implications for particle theories and phenomenological models.Our studies indicate that,with its highlighted advantages and anticipated excellent detector performance,the CEPC can explore beauty andτphysics in ways that are superior to or complementary with the Belle II and Large-Hadron-Collider-beauty experiments,potentially enabling the detection of new physics at energy scales of 10 TeV and above.This potential also extends to the observation of yet-to-be-discovered rare and exotic processes,as well as testing fundamental principles such as lepton flavor universality,lepton and baryon number conservation,etc.,making the CEPC a vibrant platform for flavor physics research.The WW threshold scan,Higgs-factory operation and top-pair productions of the CEPC further enhance its merits in this regard,especially for measuring the Cabibbo-Kobayashi-Maskawa matrix elements,and Flavor-Changing-NeutralCurrent physics of Higgs boson and top quarks.We outline the requirements for detector performance and considerations for future development to achieve the anticipated scientific goals.The role of machine learning for innovative detector design and advanced reconstruction algorithms is also stressed.The CEPC flavor physics program not only develops new capabilities for exploring flavor physics beyond existing projects but also enriches the physics opportunities of this machine.It should be remarked that,given the richness of the CEPC flavor physics,this manuscript is not meant to be a comprehensive survey,but rather an investigation of representative cases.Uncovering the full potential of flavor physics at the CEPC will require further dedicated explorations in the future.
基金Supported by NNSFC(11325525)National Recruitment Program for Young ProfessionalsCAS Center for Excellence in Particle Physics(CCEPP)
文摘In the framework of the canonical seesaw model,we present a simple but viable scenario to explicitly break an S3L×S3R flavor symmetry in the leptonic sector.It turns out that the leptonic flavor mixing matrix is completely determined by the mass ratios of the charged leptons（i.e.,me/mμand mμ/mτ） and those of light neutrinos（i.e.,m1/m2 and m2/m3）.The latest global-fit results of the three neutrino mixing angles {θ12,θ13,θ23}and two neutrino mass-squared differences {？m212,？m312} at the 3σ level are used to constrain the parameter space of {m1/m2,m2/m3}.The predictions for the mass spectrum and flavor mixing are highlighted：（1） the neutrino mass spectrum shows a hierarchical pattern and a normal ordering,e.g.,m1≈2.2meV,m2≈8.8 meV and m3≈52.7 meV;（2） only the first octant of θ23 is allowed,namely,41.8？ θ23 43.3？;（3） the Dirac C P-violating phase δ ≈-22？deviates significantly from the maximal value-90？.All these predictions are ready to be tested in ongoing and forthcoming neutrino oscillation experiments.Moreover,we demonstrate that the cosmological matter-antimatter asymmetry can be explained via resonant leptogenesis,including the individual lepton-flavor effects.In our scenario,leptonic C P violation at low-and high-energy scales is closely connected.
基金Supported by Natural Science Foundation of Shandong Province(ZR2014AM016,ZR2016AM16)National Natural Science Foundation of China(11275115,11325525,11635009)
文摘The non-relativistic wave function framework is applied to study the production and decay of exotic hadrons, which can be effectively described as bound states of other hadrons. Employing the factorized formulation,with the help of event generators, we investigate the production of exotic hadrons in multiproduction processes at high energy hadron colliders. This study provides crucial information for the measurements of the relevant exotic hadrons.
基金National Natural Science Foundation of China(11635009,11605075)Natural Science Foundation of Shandong Province(ZR2017JL006)
文摘Lepton number violation processes can be induced by the Majorana neutrino exchange, which provide evidence for the Majorana nature of neutrinos. In addition to the natural explanation of the small neutrino masses,Type-I seesaw mechanism predicts the existence of Majorana neutrinos. The aim of this work is to study the B meson rare decays B^+→K^((*))+μ^+μ^-in the Standard Model and its extensions, and then to investigate the same-sign decay process B^+→K^((*)-)μ^+μ^+. The corresponding dilepton invariant mass distributions are calculated. It is found that the dilepton angular distributions could shed light on the properties of new interactions induced by Majorana neutrinos.
基金Supported by National Natural Science Foundation of China (11775130, 11775132, 11635009, 11325525, 11875179)Natural Science Foundation of Shandong Province (ZR2016AM16, ZR2017MA002)。
文摘We calculate the masses of the QQqq(Q=c,b:q=u,d,s)tetraquark states with the aid of heavy diquark-antiquark symmetry(HDAS)and the chromomagnetic interaction(CMI)model.The masses of the highestspin(J=2)tetraquarks that have only the(QQ)(3):(qq)_(3).color structure are related with those of conventional hadrons using HDAS.Thereafter,the masses of their partner states are determined with the mass splittings in the CMI model.Our numerical results reveal that(i)the lightest ccnn(n=u,d)is an I(J^(P))=0(1^(+))state around 3929 MeV(53 MeV above the DD^(*) threshold),and none of the double-charm tetraquarks are stable;(ii)the stable double-bottom tetraquarks are the lowest 0(1^(+))bbin around 10488 MeV(≈116 MeV below the BB^(*)threshold)and the lowest 1/2(1^(+))bbns around 10671 MeV(≈20 MeV below the BB_(s)^(*)/B_(s)B^(*)threshold);and(iii)the two lowest bcnn tetraquarks,namely the lowest 0(0^(+))around 7167 MeV and the lowest 0(1)around 7223 MeV,are in the nearthreshold states.Moreover,we discuss the constraints on the masses of double-heavy hadrons.Specifically,for the lowest nonstrange tetraquarks,we obtain T_(cc)<3965 MeV,T_(bb)<10627 MeV,and T_(bc)<7199 MeV.
基金Supported by the National Natural Science Foundation of China(12235008,12275157,11905114)the Natural Science Foundation of Shandong Province,China(ZR2023MA041)。
文摘We studied the spectrum and rearrangement decays of S-wave cs■tetraquark states in a simplified quark model.The masses and widths were estimated by assuming that X(4140)is the lower 1^(++)cs■tetraquark.Comparing our results with experimental measurements,we found that X(3960),recently observed by LHCb,can be considered the lowest 0^(++)sc■tetraquark state and X0(4140)could be the second lowest 0^(++)cs■tetraquark.Predictions of ratios between partial widths for the involved tetraquarks are provided in this paper.We aim to identify more cs■tetraquarks with J^(PC)=1^(+-),0^(++),and 2^(++).
基金Supported in part by the National Natural Science Foundation of China(12235008,11875179)the Natural Science Foundation of Shandong Province,China(ZR2021QA040)。
文摘A nonzero neutrino mass may be a sign of new physics beyond the standard model(SM).To explain the small neutrino mass,we can extend the SM using right-handed Majorana neutrinos in a low-scale seesaw mechanism,and the CP violation effect can be induced due to the CP phase in the interference of heavy Majorana neutrinos.The existence of heavy Majorana neutrinos may lead to lepton number violation processes,which can be used to search for the signals of heavy Majorana neutrinos.In this paper,we focus on the CP violation effect related to two generations of heavy Majorana neutrinos at 15 GeV<m_(N1)<70 GeV in the pair production of W bosons and rare decays.It is valuable to investigate Majorana neutrino production signals and the related CP violation effects in rare W boson decays at future lepton colliders.
基金Supported in part by National Natural Science Foundation of China(11875179,11775130)Natural Science Foundation of Shandong Province(ZR2021QA040)。
文摘Heavy Majorana neutrinos beyond the standard model can simultaneously explain the origin of tiny neutRino masses and matter-antimatter asymmetry in our Universe.The existence of heavy Majorana neutrinos will also lead to lepton number violation and confirm the possibility of rare lepton-number-violating W decays.With contributions from two different Majorana neutrinos,nonzero CP asymmetry may be generated from the rate difference between W decay and its CP-conjugate process.The aim of this study is to investigate the prospects of measuring CP violation in rare w decays via Majorana neutRInos at the LHC.Our calculations show that the induced CP asymmetry is independent of the Majorana neutrino mass for 15<m_(N)<70GeV.Such a CP asymmetry,if observed,would in turn provide unambiguous evidence of new physics beyond the standard model.
基金Supported by the National Science Foundation of China(12235008,12275156,12275157,12321005)。
文摘The finite mass of the heavy quark suppresses the collimated radiations;this is generally referred to as the dead cone effect.In this paper,we study the distribution of hadron multiplicity over the hadron opening angle with respect to the jet axis for various jet flavors.The corresponding measurement can be the most straightforward and simplest approach to explore the dynamical evolution of the radiations in the corresponding jet,which can expose the mass effect.We also propose a transverse energy-weighted angular distribution,which sheds light on the interplay between perturbative and non-perturbative effects in the radiation.Through Monte-Carlo simulations,our calculations show that the dead cone effect can be clearly observed by finding the ratio between the b and light-quark(inclusive)jets;this is expected to be measured at the LHC in the future.
基金supported in part by the National Natural Science Foundation of China(11875179,11325525,11635009,11775130,11905112)the Natural Science Foundation of Shandong Province(ZR2017MA002,ZR2019QA012)the Fundamental Research Funds of Shandong University(2019GN038)
文摘Dark sector may couple to the Standard Model via one or more mediator particles.We discuss two types of mediators:the dark photon A’ and the dark scalar mediator Φ .The total cross-sections and various differential distributions of the processes e+e-→qqA’ and e+e→qqφ（q=u,d,c,s and b quarks） are discussed.We focus on the study of the invisible due to the cleaner background at future e+e-colliders.It is found that the kinematic distributions of the two-jet system could be used to identify（or exclude） the dark photon and the dark scalar mediator,as well as to distinguish between them.We further study the possibility of a search for dark photons at a future CEPC experiment with s1/2=91.2 GeV and 240 GeV.With CEPC running at s1/2=91.2 GeV,it would be possible to perform a decisive measurement of the dark photon（20 GeV <mA’ <60 GeV） in less than one operating year.The lower limits of the integrated luminosity for the significance S/B1/2=2σ,3σ and 5σ are presented.
