We have investigated production of doubly charged Higgs particles ∆ ++ L,R via W W fusion process... more We have investigated production of doubly charged Higgs particles ∆ ++ L,R via W W fusion process in proton-proton collisions at LHC energies in the framework of the leftright symmetric model. The production cross section of the right-triplet Higgs ∆ ++ R is for representative values of model parameters at femtobarn level. The discovery reach depends on the mass of the right-handed gauge boson W R . At best ∆ ++ R mass up to 2.4 TeV are achievable within one year run. For ∆ ++ L the corresponding limit is 1.75 TeV which depends on the value of the left-triplet vev v L . Comparison with Drell-Yan pair production processes shows that studies of the W W fusion processes extend the discovery reach of LHC roughly by a factor of two. The main experimental signal of a produced ∆ ++ L,R would be a hard same-sign lepton pair. There will be no substantial background due to the Standard Model (SM) interactions, since in the SM a same-sign lepton pair will always be associated with missing energy, i.e. neutrinos, due to lepton number conservation.
While the triplet-like Higgses up to a few hundred GeV masses are already excluded for a vast reg... more While the triplet-like Higgses up to a few hundred GeV masses are already excluded for a vast region of the model parameter space from the LHC searches, strikingly, there is a region of this parameter space that is beyond the reach of the existing LHC searches, and doubly/singly-charged and neutral Higgses as light as 200 GeV or even lighter are still allowed by the LHC data. We study several search strategies targeting different parts of this LHC elusive parameter space at two configurations of e − e + colliders-500 GeV and 1 TeV centre of mass energies. We find that a vast region of this parameter space could be probed with 5σ discovery with the early e − e + colliders' data.
European Physical Journal-special Topics, Dec 1, 2020
The left-right symmetric models extend the gauge group of the Standard Model enabling treatment o... more The left-right symmetric models extend the gauge group of the Standard Model enabling treatment of the left-and right-handed fermions in the same footing. The left-right symmetry requires the existence of right-handed neutrinos, leading naturally to non-zero masses for neutrinos. Here some aspects of a supersymmetric version of the leftright symmetric models are reviewed. Such models have many virtues, including possibility for dark matter without any new additional symmetry needed in order to have a stable lightest supersymmetric particle. In the model the lightest sneutrino or the lightest neutralino can form dark matter of the universe, at the same time fulfilling all the experimental constraints. The dark matter particle in the model can be very different from the dark matter typical in the minimal supersymmetric standard model. Specific signals for this kind of models at the LHC are also discussed.
The goal of this report is to summarize the current situation and discuss possible search strateg... more The goal of this report is to summarize the current situation and discuss possible search strategies for charged scalars, in non-supersymmetric extensions of the Standard Model at the LHC. Such scalars appear in Multi-Higgs-Doublet models, in particular in the popular Two-Higgs-Doublet model, allowing for charged and additional neutral Higgs bosons. These models have the attractive property that electroweak precision observables are automatically in agreement with the Standard Model at the tree level. For the most popular version of this framework, Model II, a discovery of a charged Higgs boson remains challenging, since the parameter space is becoming very constrained, and the QCD background is very high.
The charged Higgs boson is an inevitable particle in supersymmetric models, both in the minimal v... more The charged Higgs boson is an inevitable particle in supersymmetric models, both in the minimal version and in extensions. It is also a particle, which may have different decay channels depending on the scalar representations in the model, and thus it may help in identifying the model. In this talk I will consider the simplest singlet and triplet extensions of the minimal supersymmetric standard model, and in particular, describe some smoking gun signals of charged Higgs at the LHC collider. I will also comment the charged scalars in a supersymmetric left-right model.
We consider the possibility of new physics giving rise to effective interactions of the form e + ... more We consider the possibility of new physics giving rise to effective interactions of the form e + e − Hff , where f represents a charged lepton or a (light) quark q, and H the recently discovered Higgs boson. Such vertices would give contributions beyond the standard model to the Higgs production processes e + e − → H + − and e + e − → H qq at a future e + e − collider. We write the most general form for these vertices allowed by Lorentz symmetry. Assuming that such interactions contribute in addition to the standard model production processes, where the final-state fermion pair comes from the decay of the Z boson, we obtain the differential cross section for the processes e + e − → H + − and e + e − → H qq to linear order in the effective interactions. We propose several observables with differing CP and T properties which, if measured, can be used to constrain the couplings occurring in interaction vertices. We derive possible limits on these couplings that may be obtained at a collider with centre-of-mass energy of 500 GeV and an integrated luminosity of 500 fb −1. We also carry out the analysis assuming that both the electron and positron beams can be longitudinally polarized, and find that the sensitivity to the couplings can be improved by a factor of 2-4 by a specific choice of the signs of the polarizations of both the electron and positron beams for the same integrated luminosity.
The next generation neutrino observatory proposed by the LBNO collaboration will address fundamen... more The next generation neutrino observatory proposed by the LBNO collaboration will address fundamental questions in particle and astroparticle physics. The experiment consists of a far detector, in its first stage a 20 kt LAr double phase TPC and a magnetised iron calorimeter, situated at 2300 km from CERN and a near detector based on a high-pressure argon gas TPC. The long baseline provides a unique opportunity to study neutrino flavour oscillations over their 1st and 2nd oscillation maxima exploring the L/E behaviour, and distinguishing effects arising from δ CP and matter. In this paper we have reevaluated the physics potential of this setup for determining the mass hierarchy (MH) and discovering CP-violation (CPV), using a conventional neutrino beam from the CERN SPS with a power of 750 kW. We use conservative assumptions on the knowledge of oscillation parameter priors and systematic uncertainties. The impact of each systematic error and the precision of oscillation prior is shown. We demonstrate that the first stage of LBNO can determine unambiguously the MH to > 5σ C.L. over the whole phase space. We show that the statistical treatment of the experiment is of very high importance, resulting in the conclusion that LBNO has ∼ 100% probability to determine the MH in at most 4-5 years of running. Since the knowledge of MH is indispensable to extract δ CP from the data, the first LBNO phase can convincingly give evidence for CPV on the 3σ C.L. using today's knowledge on oscillation parameters and realistic assumptions on the systematic uncertainties.
We study the production of (t +t)g at the hadron colliders in an R-parity (R p) violating supersy... more We study the production of (t +t)g at the hadron colliders in an R-parity (R p) violating supersymmetric model. This process provides us with information not only about R p violation, but may also help us in detecting the supersymmetry itself. It is possible to detect an R p violating signal (with single gluino production) at the future hadron colliders, such as Fermilab Tevatron Run II or CERN Large Hadron Collider (LHC), if the parameters in the supersymmetric / R p interactions are not too small, e.g. for mg = 1 TeV, λ ′′ = 0.1, still hundreds of events are produced at LHC with luminosity 30 f b −1. Even if we could not detect a signal of / R p in the experiment, we get stringent constraints on the heavy flavour / R p couplings. In addition to the minimal supersymmetric standard model we have also considered some models with a heavy gluino as the lightest supersymmetric particle.
The International Linear Collider (ILC) is on the table now as a new global energyfrontier accele... more The International Linear Collider (ILC) is on the table now as a new global energyfrontier accelerator laboratory taking data in the 2030's. The ILC addresses key questions for our current understanding of particle physics. It is based on a proven accelerator technology. Its experiments will challenge the Standard Model of particle physics and will provide a new window to look beyond it. This document brings the story of the ILC up to date, emphasizing its strong physics motivation, its readiness for construction, and the opportunity it presents to the US and the global particle physics community.
The recently proposed multi-phase criticality principle in Coleman-Weinberg models can provide a ... more The recently proposed multi-phase criticality principle in Coleman-Weinberg models can provide a new explanation for the hierarchy between the electroweak and new physics scales. When applied to the Standard Model, a Higgs boson as light as the pseudo-Goldstone boson of broken scale invariance occurs. The suppressed mixing between the two light fields still carries information about the large scale of symmetry breaking, albeit up to logarithmic corrections. In this work we probe this scenario with the present LHC data and assess the impact of future lepton and hadron colliders. Our results show that the multi-phase criticality can easily explain the apparent absence of new physics at the energy scales tested in current experiments. 1 The possible appearance of two degenerate minima in the SM Higgs potential [16], which sometimes is also called criticality, should not be confused with our framework of multi-phase criticality.
The COSINUS (Cryogenic Observatory for SIgnatures seen in Next-generation Underground Searches) e... more The COSINUS (Cryogenic Observatory for SIgnatures seen in Next-generation Underground Searches) experiment aims at the detection of dark matter-induced recoils in sodium iodide (NaI) crystals operated as scintillating cryogenic calorimeters. The detection of both scintillation light and phonons allows performing an event-by-event signal to background discrimination, thus enhancing the sensitivity of the experiment. The choice of using NaI crystals is motivated by the goal of probing the long-standing DAMA/LIBRA results using the same target material. The construction of the experimental facility is foreseen to start by 2021 at the INFN Gran Sasso National Laboratory (LNGS) in Italy. It consists of a cryostat housing the target crystals shielded from the external radioactivity by a water tank acting, at the same time, as an active veto against cosmic ray-induced events. Taking into account both environmental radioactivity and intrinsic contamination of materials used for cryostat, sh...
We consider a neutrinophilic Higgs scenario where the Standard Model is extended by one additiona... more We consider a neutrinophilic Higgs scenario where the Standard Model is extended by one additional Higgs doublet and three generations of singlet right-handed Majorana neutrinos. Light neutrino masses are generated through mixing with the heavy neutrinos via Type-I seesaw mechanism when the neutrinophilic Higgs gets a vacuum expectation value (VEV). The Dirac neutrino Yukawa coupling in this scenario can be sizable compared to those in the canonical Type-I seesaw mechanism owing to the small neutrinophilic Higgs VEV giving rise to interesting phenomenological consequences. We have explored various signal regions likely to provide a hint of such a scenario at the LHC as well as at future $e^+e^-$ colliders. We have also highlighted the consequences of light neutrino mass hierarchies in collider phenomenology that can complement the findings of neutrino oscillation experiments.
This is the third out of five chapters of the final report [1] of the Workshop on Physics at HL-L... more This is the third out of five chapters of the final report [1] of the Workshop on Physics at HL-LHC, and perspectives on HE-LHC [2]. It is devoted to the study of the potential, in the search for Beyond the Standard Model (BSM) physics, of the High Luminosity (HL) phase of the LHC, defined as 3 ab−1 of data taken at a centre-of-mass energy of 14 TeV, and of a possible future upgrade, the High Energy (HE) LHC, defined as 15 ab−1 of data at a centre-of-mass energy of 27 TeV. We consider a large variety of new physics models, both in a simplified model fashion and in a more model-dependent one. A long list of contributions from the theory and experimental (ATLAS, CMS, LHCb) communities have been collected and merged together to give a complete, wide, and consistent view of future prospects for BSM physics at the considered colliders. On top of the usual standard candles, such as supersymmetric simplified models and resonances, considered for the evaluation of future collider potentials...
We have explored the prospect of probing a neutral scalar ($H$) produced in association with one ... more We have explored the prospect of probing a neutral scalar ($H$) produced in association with one $b$-quark and decaying either invisibly or into a pair of $b$-quarks at the LHC with centre of mass energy $\sqrt s = 14$ TeV. In this regard, we adopt an effective theory approach to parameterize a $Hb\bar bg$ vertex arising from a dimension six operator that encompasses the effect of some new physics setting in at a high scale. We concentrate solely on the five-flavor scheme to ascertain the sensitivity of the 14 TeV LHC in probing such an effective coupling as a function of the scalar mass at the highest possible projected luminosity, $3000~{\rm fb}^{-1}$. Through our multivariate analysis using machine learning algorithm we show that staying within the perturbative limit of the Wilson coefficient of the effective interaction, evidence with statistical significance of $3\sigma$ can be obtained in two different signal regions for $m_H\lesssim 2$ TeV and the scale of new physics $\Lambd...
ATLAS and CMS have reported an excess in the flavor violating decay of the Higgs boson, $h \right... more ATLAS and CMS have reported an excess in the flavor violating decay of the Higgs boson, $h \rightarrow \mu \tau$. We show that this result can be accommodated through a mixing of the Higgs with a flavon, the field responsible for generating the Yukawa matrices in the lepton sector. We employ a version of the Froggatt-Nielsen mechanism at the electroweak scale, with only the leptons and the flavon transforming non--trivially under the corresponding symmetry group. Non--observation of charged lepton flavor violation (LFV) in other processes imposes important constraints on the model, which we find to be satisfied in substantial regions of parameter space.
The Compact Linear Collider (CLIC) is a TeV-scale high-luminosity linear $e^+e^−$ collider under ... more The Compact Linear Collider (CLIC) is a TeV-scale high-luminosity linear $e^+e^−$ collider under development at CERN. Following the CLIC conceptual design published in 2012, this report provides an overview of the CLIC project, its current status, and future developments. It presents the CLIC physics potential and reports on design, technology, and implementation aspects of the accelerator and the detector. For an optimal exploitation of its physics potential, CLIC is foreseen to be built and operated in stages, at centre-of-mass energies of 380 GeV, 1.5 TeV and 3 TeV, respectively, for a site length ranging from 11 km to 50 km. CLIC uses a two-beam acceleration scheme, in which normal-conducting high-gradient 12 GHz accelerating structures are powered via a high-current drive beam. For the first stage, an alternative with X-band klystron powering is also considered. CLIC accelerator optimisation, technical developments and system tests have resulted in significant progress in recen...
We have investigated production of doubly charged Higgs particles ∆ ++ L,R via W W fusion process... more We have investigated production of doubly charged Higgs particles ∆ ++ L,R via W W fusion process in proton-proton collisions at LHC energies in the framework of the leftright symmetric model. The production cross section of the right-triplet Higgs ∆ ++ R is for representative values of model parameters at femtobarn level. The discovery reach depends on the mass of the right-handed gauge boson W R . At best ∆ ++ R mass up to 2.4 TeV are achievable within one year run. For ∆ ++ L the corresponding limit is 1.75 TeV which depends on the value of the left-triplet vev v L . Comparison with Drell-Yan pair production processes shows that studies of the W W fusion processes extend the discovery reach of LHC roughly by a factor of two. The main experimental signal of a produced ∆ ++ L,R would be a hard same-sign lepton pair. There will be no substantial background due to the Standard Model (SM) interactions, since in the SM a same-sign lepton pair will always be associated with missing energy, i.e. neutrinos, due to lepton number conservation.
While the triplet-like Higgses up to a few hundred GeV masses are already excluded for a vast reg... more While the triplet-like Higgses up to a few hundred GeV masses are already excluded for a vast region of the model parameter space from the LHC searches, strikingly, there is a region of this parameter space that is beyond the reach of the existing LHC searches, and doubly/singly-charged and neutral Higgses as light as 200 GeV or even lighter are still allowed by the LHC data. We study several search strategies targeting different parts of this LHC elusive parameter space at two configurations of e − e + colliders-500 GeV and 1 TeV centre of mass energies. We find that a vast region of this parameter space could be probed with 5σ discovery with the early e − e + colliders' data.
European Physical Journal-special Topics, Dec 1, 2020
The left-right symmetric models extend the gauge group of the Standard Model enabling treatment o... more The left-right symmetric models extend the gauge group of the Standard Model enabling treatment of the left-and right-handed fermions in the same footing. The left-right symmetry requires the existence of right-handed neutrinos, leading naturally to non-zero masses for neutrinos. Here some aspects of a supersymmetric version of the leftright symmetric models are reviewed. Such models have many virtues, including possibility for dark matter without any new additional symmetry needed in order to have a stable lightest supersymmetric particle. In the model the lightest sneutrino or the lightest neutralino can form dark matter of the universe, at the same time fulfilling all the experimental constraints. The dark matter particle in the model can be very different from the dark matter typical in the minimal supersymmetric standard model. Specific signals for this kind of models at the LHC are also discussed.
The goal of this report is to summarize the current situation and discuss possible search strateg... more The goal of this report is to summarize the current situation and discuss possible search strategies for charged scalars, in non-supersymmetric extensions of the Standard Model at the LHC. Such scalars appear in Multi-Higgs-Doublet models, in particular in the popular Two-Higgs-Doublet model, allowing for charged and additional neutral Higgs bosons. These models have the attractive property that electroweak precision observables are automatically in agreement with the Standard Model at the tree level. For the most popular version of this framework, Model II, a discovery of a charged Higgs boson remains challenging, since the parameter space is becoming very constrained, and the QCD background is very high.
The charged Higgs boson is an inevitable particle in supersymmetric models, both in the minimal v... more The charged Higgs boson is an inevitable particle in supersymmetric models, both in the minimal version and in extensions. It is also a particle, which may have different decay channels depending on the scalar representations in the model, and thus it may help in identifying the model. In this talk I will consider the simplest singlet and triplet extensions of the minimal supersymmetric standard model, and in particular, describe some smoking gun signals of charged Higgs at the LHC collider. I will also comment the charged scalars in a supersymmetric left-right model.
We consider the possibility of new physics giving rise to effective interactions of the form e + ... more We consider the possibility of new physics giving rise to effective interactions of the form e + e − Hff , where f represents a charged lepton or a (light) quark q, and H the recently discovered Higgs boson. Such vertices would give contributions beyond the standard model to the Higgs production processes e + e − → H + − and e + e − → H qq at a future e + e − collider. We write the most general form for these vertices allowed by Lorentz symmetry. Assuming that such interactions contribute in addition to the standard model production processes, where the final-state fermion pair comes from the decay of the Z boson, we obtain the differential cross section for the processes e + e − → H + − and e + e − → H qq to linear order in the effective interactions. We propose several observables with differing CP and T properties which, if measured, can be used to constrain the couplings occurring in interaction vertices. We derive possible limits on these couplings that may be obtained at a collider with centre-of-mass energy of 500 GeV and an integrated luminosity of 500 fb −1. We also carry out the analysis assuming that both the electron and positron beams can be longitudinally polarized, and find that the sensitivity to the couplings can be improved by a factor of 2-4 by a specific choice of the signs of the polarizations of both the electron and positron beams for the same integrated luminosity.
The next generation neutrino observatory proposed by the LBNO collaboration will address fundamen... more The next generation neutrino observatory proposed by the LBNO collaboration will address fundamental questions in particle and astroparticle physics. The experiment consists of a far detector, in its first stage a 20 kt LAr double phase TPC and a magnetised iron calorimeter, situated at 2300 km from CERN and a near detector based on a high-pressure argon gas TPC. The long baseline provides a unique opportunity to study neutrino flavour oscillations over their 1st and 2nd oscillation maxima exploring the L/E behaviour, and distinguishing effects arising from δ CP and matter. In this paper we have reevaluated the physics potential of this setup for determining the mass hierarchy (MH) and discovering CP-violation (CPV), using a conventional neutrino beam from the CERN SPS with a power of 750 kW. We use conservative assumptions on the knowledge of oscillation parameter priors and systematic uncertainties. The impact of each systematic error and the precision of oscillation prior is shown. We demonstrate that the first stage of LBNO can determine unambiguously the MH to > 5σ C.L. over the whole phase space. We show that the statistical treatment of the experiment is of very high importance, resulting in the conclusion that LBNO has ∼ 100% probability to determine the MH in at most 4-5 years of running. Since the knowledge of MH is indispensable to extract δ CP from the data, the first LBNO phase can convincingly give evidence for CPV on the 3σ C.L. using today's knowledge on oscillation parameters and realistic assumptions on the systematic uncertainties.
We study the production of (t +t)g at the hadron colliders in an R-parity (R p) violating supersy... more We study the production of (t +t)g at the hadron colliders in an R-parity (R p) violating supersymmetric model. This process provides us with information not only about R p violation, but may also help us in detecting the supersymmetry itself. It is possible to detect an R p violating signal (with single gluino production) at the future hadron colliders, such as Fermilab Tevatron Run II or CERN Large Hadron Collider (LHC), if the parameters in the supersymmetric / R p interactions are not too small, e.g. for mg = 1 TeV, λ ′′ = 0.1, still hundreds of events are produced at LHC with luminosity 30 f b −1. Even if we could not detect a signal of / R p in the experiment, we get stringent constraints on the heavy flavour / R p couplings. In addition to the minimal supersymmetric standard model we have also considered some models with a heavy gluino as the lightest supersymmetric particle.
The International Linear Collider (ILC) is on the table now as a new global energyfrontier accele... more The International Linear Collider (ILC) is on the table now as a new global energyfrontier accelerator laboratory taking data in the 2030's. The ILC addresses key questions for our current understanding of particle physics. It is based on a proven accelerator technology. Its experiments will challenge the Standard Model of particle physics and will provide a new window to look beyond it. This document brings the story of the ILC up to date, emphasizing its strong physics motivation, its readiness for construction, and the opportunity it presents to the US and the global particle physics community.
The recently proposed multi-phase criticality principle in Coleman-Weinberg models can provide a ... more The recently proposed multi-phase criticality principle in Coleman-Weinberg models can provide a new explanation for the hierarchy between the electroweak and new physics scales. When applied to the Standard Model, a Higgs boson as light as the pseudo-Goldstone boson of broken scale invariance occurs. The suppressed mixing between the two light fields still carries information about the large scale of symmetry breaking, albeit up to logarithmic corrections. In this work we probe this scenario with the present LHC data and assess the impact of future lepton and hadron colliders. Our results show that the multi-phase criticality can easily explain the apparent absence of new physics at the energy scales tested in current experiments. 1 The possible appearance of two degenerate minima in the SM Higgs potential [16], which sometimes is also called criticality, should not be confused with our framework of multi-phase criticality.
The COSINUS (Cryogenic Observatory for SIgnatures seen in Next-generation Underground Searches) e... more The COSINUS (Cryogenic Observatory for SIgnatures seen in Next-generation Underground Searches) experiment aims at the detection of dark matter-induced recoils in sodium iodide (NaI) crystals operated as scintillating cryogenic calorimeters. The detection of both scintillation light and phonons allows performing an event-by-event signal to background discrimination, thus enhancing the sensitivity of the experiment. The choice of using NaI crystals is motivated by the goal of probing the long-standing DAMA/LIBRA results using the same target material. The construction of the experimental facility is foreseen to start by 2021 at the INFN Gran Sasso National Laboratory (LNGS) in Italy. It consists of a cryostat housing the target crystals shielded from the external radioactivity by a water tank acting, at the same time, as an active veto against cosmic ray-induced events. Taking into account both environmental radioactivity and intrinsic contamination of materials used for cryostat, sh...
We consider a neutrinophilic Higgs scenario where the Standard Model is extended by one additiona... more We consider a neutrinophilic Higgs scenario where the Standard Model is extended by one additional Higgs doublet and three generations of singlet right-handed Majorana neutrinos. Light neutrino masses are generated through mixing with the heavy neutrinos via Type-I seesaw mechanism when the neutrinophilic Higgs gets a vacuum expectation value (VEV). The Dirac neutrino Yukawa coupling in this scenario can be sizable compared to those in the canonical Type-I seesaw mechanism owing to the small neutrinophilic Higgs VEV giving rise to interesting phenomenological consequences. We have explored various signal regions likely to provide a hint of such a scenario at the LHC as well as at future $e^+e^-$ colliders. We have also highlighted the consequences of light neutrino mass hierarchies in collider phenomenology that can complement the findings of neutrino oscillation experiments.
This is the third out of five chapters of the final report [1] of the Workshop on Physics at HL-L... more This is the third out of five chapters of the final report [1] of the Workshop on Physics at HL-LHC, and perspectives on HE-LHC [2]. It is devoted to the study of the potential, in the search for Beyond the Standard Model (BSM) physics, of the High Luminosity (HL) phase of the LHC, defined as 3 ab−1 of data taken at a centre-of-mass energy of 14 TeV, and of a possible future upgrade, the High Energy (HE) LHC, defined as 15 ab−1 of data at a centre-of-mass energy of 27 TeV. We consider a large variety of new physics models, both in a simplified model fashion and in a more model-dependent one. A long list of contributions from the theory and experimental (ATLAS, CMS, LHCb) communities have been collected and merged together to give a complete, wide, and consistent view of future prospects for BSM physics at the considered colliders. On top of the usual standard candles, such as supersymmetric simplified models and resonances, considered for the evaluation of future collider potentials...
We have explored the prospect of probing a neutral scalar ($H$) produced in association with one ... more We have explored the prospect of probing a neutral scalar ($H$) produced in association with one $b$-quark and decaying either invisibly or into a pair of $b$-quarks at the LHC with centre of mass energy $\sqrt s = 14$ TeV. In this regard, we adopt an effective theory approach to parameterize a $Hb\bar bg$ vertex arising from a dimension six operator that encompasses the effect of some new physics setting in at a high scale. We concentrate solely on the five-flavor scheme to ascertain the sensitivity of the 14 TeV LHC in probing such an effective coupling as a function of the scalar mass at the highest possible projected luminosity, $3000~{\rm fb}^{-1}$. Through our multivariate analysis using machine learning algorithm we show that staying within the perturbative limit of the Wilson coefficient of the effective interaction, evidence with statistical significance of $3\sigma$ can be obtained in two different signal regions for $m_H\lesssim 2$ TeV and the scale of new physics $\Lambd...
ATLAS and CMS have reported an excess in the flavor violating decay of the Higgs boson, $h \right... more ATLAS and CMS have reported an excess in the flavor violating decay of the Higgs boson, $h \rightarrow \mu \tau$. We show that this result can be accommodated through a mixing of the Higgs with a flavon, the field responsible for generating the Yukawa matrices in the lepton sector. We employ a version of the Froggatt-Nielsen mechanism at the electroweak scale, with only the leptons and the flavon transforming non--trivially under the corresponding symmetry group. Non--observation of charged lepton flavor violation (LFV) in other processes imposes important constraints on the model, which we find to be satisfied in substantial regions of parameter space.
The Compact Linear Collider (CLIC) is a TeV-scale high-luminosity linear $e^+e^−$ collider under ... more The Compact Linear Collider (CLIC) is a TeV-scale high-luminosity linear $e^+e^−$ collider under development at CERN. Following the CLIC conceptual design published in 2012, this report provides an overview of the CLIC project, its current status, and future developments. It presents the CLIC physics potential and reports on design, technology, and implementation aspects of the accelerator and the detector. For an optimal exploitation of its physics potential, CLIC is foreseen to be built and operated in stages, at centre-of-mass energies of 380 GeV, 1.5 TeV and 3 TeV, respectively, for a site length ranging from 11 km to 50 km. CLIC uses a two-beam acceleration scheme, in which normal-conducting high-gradient 12 GHz accelerating structures are powered via a high-current drive beam. For the first stage, an alternative with X-band klystron powering is also considered. CLIC accelerator optimisation, technical developments and system tests have resulted in significant progress in recen...
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Papers by Katri Huitu