ILC Document Server
http://ilcdoc.linearcollider.org
ILC Document Server latest documentsenSun, 31 Jul 2016 00:17:23 GMTInvenio 1.0.7.2-5776ilcdoc-support@linearcollider.org36050043125http://ilcdoc.linearcollider.org/img/site_logo_rss.pngILC Document Server
http://ilcdoc.linearcollider.org
Search Search this site:p
http://ilcdoc.linearcollider.org/search
FCNC decays of SM fermions into a dark photon
http://ilcdoc.linearcollider.org/record/63113
We analyze a new class of FCNC processes, the $f \to f^{\prime} \, \bar{\gamma}$ decays of a fermion $f$ into a lighter (same-charge) fermion $f^{\prime}$ plus a {\it massless} neutral vector boson, a {\it dark photon} $\bar{\gamma}$. A massless dark photon does not interact at tree level with observable fields, and the $f \!\to\! f^{\prime} \, \bar{\gamma}$ decay presents a characteristic signature where the final fermion $f^{\prime}$ is balanced by a {\it massless invisible} system. Models recently proposed to explain the exponential spread in the standard-model Yukawa couplings can indeed foresee an extra unbroken {\it dark} $U(1)$ gauge group, and the possibility to couple on-shell dark photons to standard-model fermions via one-loop magnetic-dipole kind of FCNC interactions. The latter are suppressed by the characteristic scale related to the mass of heavy messengers, connecting the standard-model particles to the dark sector. We compute the corresponding decay rates for the top, bottom, and charm decays ($t\to c\, \bar{\gamma},u\, \bar{\gamma}$, $\;b\to s\, \bar{\gamma},d\, \bar{\gamma}$, and $c\to u \bar{\gamma}$), and for the charged-lepton decays ($\tau \to \mu\, \bar{\gamma}, e\, \bar{\gamma}$, and $\mu \to e \bar{\gamma}$) in terms of model parameters. We find that large branching ratios for both quark and lepton decays are allowed in case the messenger masses are in the discovery range of the LHC. Implications of these new decay channels at present and future collider experiments are briefly discussed.Gabrielli, EmidioThu, 21 Jul 2016 06:28:51 GMThttp://ilcdoc.linearcollider.org/record/631132016Lepton flavor violating Z decays: A promising window to low scale seesaw neutrinos
http://ilcdoc.linearcollider.org/record/63112
In this paper we study the Lepton Flavor Violating $Z$ boson decays $Z \to \tau \mu$ and $Z \to \tau e$ in the context of low scale seesaw models with new heavy Majorana neutrinos whose masses could be reachable at the LHC. Our computations of the decay rates are done in the particular realization given by the Inverse Seesaw Model with six extra heavy neutrinos which are quasi-degenerate in three pseudo-Dirac pairs. In particular, we focus on scenarios that are built ad-hoc to produce suppressed rates in all the processes involving $\mu$-$e$ transitions, given the fact that these are by far the most strongly constrained by present data. We will fully explore the $Z \to \tau \mu$ and $Z \to \tau e$ rates, together with a set of observables that we find to be the most constraining ones, and we will conclude that sizable rates of up to $2 \times 10^{-7}$, accessible at future colliders, can be reached in this model for Majorana masses in the few TeV range, potentially reachable at LHC.De Romeri, VTue, 19 Jul 2016 06:25:19 GMThttp://ilcdoc.linearcollider.org/record/631122016One-Loop Radiative Correction to the Triple Higgs Coupling in the Higgs Singlet Model
http://ilcdoc.linearcollider.org/record/63111
Though the 125 GeV Higgs boson is consistent with the standard model (SM) prediction until now, the triple coupling can deviate from the SM value in the physics beyond the SM (BSM). In this paper, the radiative correction to the triple Higgs coupling is calculated in the minimal extension of the SM by adding a real gauge singlet scalar. In this model there are two scalars $h$ and $H$ and both of them are mixed states of the doublet and singlet. Provided that the mixing angle is set to be zero, $h$ is the pure left-over of the doublet and its behavior is the same as that of the SM except the triple $h$ couping. In this SM limit case, the effect of the singlet $H$ will decouple from the fermions and gauge bosons, and firstly shown up in the triple $h$ coupling. Our numerical results show that the deviation is sizable. For $\lambda_{\Phi{S}}=1$ (see text for the parameter definition), the deviation $\delta_{hhh}^{(1)}$ can be $40\%$. For $\lambda_{\Phi{S}}=1.5$, the $\delta_{hhh}^{(1)}$ can reach $140\%$. The sizable radiative correction is mainly caused by three reasons: the magnitude of the coupling $\lambda_{\Phi{S}}$, light mass of the additional scalar and the threshold enhancement. In the optimal case, the triple $h$ coupling is very sensitive to the BSM physics, and this model can be tested at future high luminosity hadron colliders and electron-positron colliders.He, Shi-PingMon, 18 Jul 2016 06:23:34 GMThttp://ilcdoc.linearcollider.org/record/631112016750 GeV diphoton resonance at the ILC
http://ilcdoc.linearcollider.org/record/63110
In this paper we study the direct production of the diphoton resonance $X$ which has been suggested by 2015 data at the LHC, in $e^+e^-\to X\gamma/XZ$ processes at the ILC. We derive an analytic expression for the scattering amplitudes of these processes, and present a comprehensive analysis for determining the properties of $X$ at the ILC. A realistic simulation study for $e^+e^-\to X\gamma$ is performed based on the full detector simulation to demonstrate the capabilities of the ILC experiment. Complementary to the searches at the LHC, prospects of the measurement of the absolute values of production cross-section are obtained for the ILC using recoil technique without assuming decay modes of $X$. In addition, we have studied the searches for $X\to\rm{invisible}$ and $X\to b\bar{b}$ modes, which are challenging at the LHC, and found that these decay modes can be discovered with high significance if their branching ratios are large enough.Fujii, KeisukeFri, 15 Jul 2016 06:18:04 GMThttp://ilcdoc.linearcollider.org/record/631102016Implications of the 750 GeV gamma-gamma Resonance as a Case Study for the International Linear Collider
http://ilcdoc.linearcollider.org/record/63109
If the gamma-gamma resonance at 750 GeV suggested by 2015 LHC data turns out to be a real effect, what are the implications for the physics case and upgrade path of the International Linear Collider? Whether or not the resonance is confirmed, this question provides an interesting case study testing the robustness of the ILC physics case. In this note, we address this question with two points: (1) Almost all models proposed for the new 750 GeV particle require additional new particles with electroweak couplings. The key elements of the 500 GeV ILC physics program---precision measurements of the Higgs boson, the top quark, and 4-fermion interactions---will powerfully discriminate among these models. This information will be important in conjunction with new LHC data, or alone, if the new particles accompanying the 750 GeV resonance are beyond the mass reach of the LHC. (2) Over a longer term, the energy upgrade of the ILC to 1 TeV already discussed in the ILC TDR will enable experiments in gamma-gamma and e+e- collisions to directly produce and study the 750 GeV particle from these unique initial states.Fujii, KeisukeThu, 14 Jul 2016 06:16:25 GMThttp://ilcdoc.linearcollider.org/record/631092016Prospects for charged Higgs searches at the LHC
http://ilcdoc.linearcollider.org/record/63108
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 (MHDM), in particular in the popular Two-Higgs-Doublet model (2HDM), allowing for charged and more 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. We also briefly comment on models with dark matter which constrain the corresponding charged scalars that occur in these models. The stakes of a possible discovery of an extended scalar sector are very high, and these searches should be pursued in all conceivable channels, at the LHC and at future colliders.Akeroyd, A GTue, 12 Jul 2016 06:14:52 GMThttp://ilcdoc.linearcollider.org/record/631082016Clues on the Majorana scale from scalar resonances at the LHC
http://ilcdoc.linearcollider.org/record/63107
In order to address the observation of the neutrino oscillations and the metastability of the Standard Model, we extend the fermion sector with two right-handed (i.e. sterile) neutrinos, and the scalar sector of the SM with a real scalar, the Hill field. The latter takes the role of a Majoron and generates the Majorana masses for the neutrino sector, such that the particle spectrum features two CP-even scalars $h_1$ and $h_2$, and also two heavy, mass degenerate neutrinos. When the $h_1$ is identified with the scalar resonance at ~125 GeV and the condition is imposed that the $h_1$ self coupling and its running vanish at the Planck scale, the scalar mixing and the vacuum expectation value of the Hill field are fixed by the $h_2$ mass. The $h_2$ can be searched for at the LHC, and it has prospects of being discovered for the target integrated luminosities of the HL-LHC and the Future Circular hadron Collider (FCC-hh) when its mass is on the weak scale. The knowledge of the $h_2$ mass and its decay properties can yield an insight into its coupling to the heavy neutrinos, and thus also on the heavy neutrino mass scale. This yields an interesting connection between potentially detectable heavy scalars in high-energy proton collisions and the mass scale of the heavy neutrinos that is testable at the LHC and at future colliders.Fischer, OliverTue, 12 Jul 2016 06:14:52 GMThttp://ilcdoc.linearcollider.org/record/631072016Dirac vs Majorana gauginos at a 100 TeV collider
http://ilcdoc.linearcollider.org/record/63106
We compare the prospects for observing theories with Majorana or Dirac gauginos at a future 100 TeV proton-proton collider. Calculating the expected discovery and exclusion regions, we find that for heavy gluino masses the squark discovery reach is significantly reduced in Dirac gluino models relative to the Majorana case. However, if the squark and gluino masses are close the reach is similar in both scenarios. We also consider the electroweak fine tuning of theories observable at such a collider, and the impact of existing constraints from flavour and CP violating observables. Models with Majorana gluinos that are fine tuned to less than one part in 10,000 can typically be discovered or excluded, and Dirac models with tuning of one part in 1,000 can be probed. The flavour structure of Majorana models is highly constrained if they have observable squarks, while O(1) violation is possible in accessible Dirac models. In both cases new sources of CP violation must be very suppressed. Future collider searches can also give important information on possible dark matter candidates. We study the relation of this to indirect and direct detection searches, and find that if dark matter is a neutralino, a 100 TeV collider could probe the viable dark matter candidates in large classes of both Dirac and Majorana models.di Cortona, Giovanni GrilliTue, 12 Jul 2016 06:14:51 GMThttp://ilcdoc.linearcollider.org/record/631062016Charged Higgs Boson Production at e+e- Colliders in the Complex MSSM: A Full One-Loop Analysis
http://ilcdoc.linearcollider.org/record/63105
For the search for additional Higgs bosons in the Minimal Supersymmetric Standard Model (MSSM) as well as for future precision analyses in the Higgs sector precise knowledge of their production properties is mandatory. We evaluate the cross sections for the charged Higgs boson production at e+e- colliders in the MSSM with complex parameters (cMSSM). The evaluation is based on a full one-loop calculation of the production mechanism e+e- -> H+H- and e+e- -> H^\pm W^\mp, including soft and hard QED radiation. The dependence of the Higgs boson production cross sections on the relevant cMSSM parameters is analyzed numerically. We find sizable contributions to many cross sections. They are, depending on the production channel, roughly of 5-10% of the tree-level results, but can go up to 20% or higher. The full one-loop contributions are important for a future linear e+e- collider such as the ILC or CLIC.Heinemeyer, STue, 12 Jul 2016 06:14:51 GMThttp://ilcdoc.linearcollider.org/record/631052016Search for anomalous quartic $ZZ\gamma\gamma$ couplings in photon-photon collisions
http://ilcdoc.linearcollider.org/record/63104
The self-couplings of the electroweak gauge bosons are completely specified by the non-Abelian gauge nature of the Standard Model (SM). The direct study of these couplings provides a significant opportunity to test the validity of the SM and the existence of new physics beyond the SM up to the high energy scale. For this reason, we investigate the potential of the processes $\gamma\gamma\rightarrow ZZ$, $e^{-}\gamma\rightarrow e^{-}\gamma^{*}\gamma \rightarrow e^{-}Z\, Z$ and $e^{+}e^{-}\rightarrow e^{+}\gamma^{*} \gamma^{*} e^{-} \rightarrow e^{+}\, Z\, Z\, e^{-}$ to examine the anomalous quartic couplings of $ZZ\gamma\gamma$ vertex at the Compact Linear Collider (CLIC) with center-of-mass energies $0.35, 1.4$ and $3$ TeV. We calculate $95\%$ confidence level sensitivities on the dimension-8 parameters with various values of the integrated luminosity. We show that the best bounds on the anomalous $\frac{f_{M2}}{\Lambda^{4}}$, $\frac{f_{M3}}{\Lambda^{4}}$, $\frac{f_{T0}}{\Lambda^4}$ and $\frac{f_{T9}}{\Lambda^4}$ couplings among three processes at center-of-mass energy of 3 TeV and integrated luminosity of $L_{int}=2000$ fb$^{-1}$ are found $[-3.30;3.30]\times 10 ^{-3}$ TeV$^{-4}$, $[-1.20;1.20]\times 10 ^{-2}$ TeV$^{-4}$, $[-3.40;3.40]\times 10 ^{-3}$ TeV$^{-4}$ and $[-1.80;1.80]\times 10 ^{-3}$ TeV$^{-4}$, respectively.Köksal, MTue, 12 Jul 2016 06:14:51 GMThttp://ilcdoc.linearcollider.org/record/631042016Higgs bosons production and decay at future $e^+e^-$ linear colliders as a probe of the B-L model
http://ilcdoc.linearcollider.org/record/63103
We study the phenomenology of the light and heavy Higgs boson production and decay in the context of a $U(1)_{B-L}$ extension of the Standard Model with an additional $Z'$ boson at future $e^+e^-$ linear colliders with center-of-mass energies of $\sqrt{s}=500-3000\hspace{0.8mm}GeV$ and integrated luminosities of ${\cal L}=500-2000\hspace{0.8mm}fb^{-1}$. The study includes the processes $e^{+}e^{-}\rightarrow (Z, Z') \to Zh$ and $e^{+}e^{-}\rightarrow (Z, Z') \to ZH$, considering both the resonant and non-resonant effects. We find that the total number of expected $Zh$ and $ZH$ events can reach 909,124 and 97,487, respectively, which is a very optimistic scenario and thus it would be possible to perform precision measurements for both Higgs bosons $h$ and $H$, as well as for the $Z'$ boson in future high-energy and high-luminosity $e^+e^-$ colliders experiments. Our study complements other studies on the B-L model and on the Higgs-strahlung processes $e^{+}e^{-}\rightarrow (Z, Z') \to Zh$ and $e^{+}e^{-}\rightarrow (Z, Z') \to ZH$.Ramirez-Sanchez, FTue, 12 Jul 2016 06:14:51 GMThttp://ilcdoc.linearcollider.org/record/631032016Precision gaugino mass measurements as a probe of large trilinear soft terms at ILC
http://ilcdoc.linearcollider.org/record/63102
In supersymmetric models with radiatively-driven naturalness, higgsino-like electroweak-inos (EW-inos) are expected to lie in a mass range 100--300 GeV, the lighter the more natural. Such states can be pair-produced at high rates at ILC where their masses are nearly equal to the value of the superpotential mu parameter while their mass splittings depend on the gaugino masses M_1 and M_2. The gaugino masses in turn depend on trilinear soft terms---the A parameters, which are expected to lie in the multi-TeV range owing to the 125 GeV Higgs mass---via two-loop contributions to renormalization group running. We examine the extent to which ILC is sensitive to large A-terms via precision EW-ino mass measurement. Extraction of gaugino masses at the percent level should allow for interesting probes of large trilinear soft SUSY breaking terms under the assumption of unified gaugino masses.Bae, Kyu JungTue, 12 Jul 2016 06:14:51 GMThttp://ilcdoc.linearcollider.org/record/631022016Measuring the trilinear neutral Higgs boson couplings in the minimal supersymmetric standard model at $e^+ e^-$ colliders in the light of the discovery of a Higgs boson
http://ilcdoc.linearcollider.org/record/63101
We consider the measurement of the trilinear couplings of the neutral Higgs bosons in the Minimal Supersymmetric Standard Model~(MSSM) at a high energy $e^+ e^-$ linear collider in the light of the discovery of a Higgs boson at the CERN Large Hadron Collider~(LHC). We identify the state observed at the LHC with the lightest Higgs boson~($h^0$) of the MSSM, and impose the constraints following from this identification, as well as other experimental constraints on the MSSM parameter space. In order to measure trilinear neutral Higgs couplings, we consider different processes where the heavier Higgs boson ($H^0$) of the MSSM is produced in electron-positron collisions, which subsequently decays into a pair of lighter Higgs bosons. We identify the regions of the MSSM parameter space where it may be possible to measure the trilinear couplings of the Higgs boson at a future electron-positron collider. A measurement of the trilinear Higgs couplings is a crucial step in the construction of the Higgs potential, and hence in establishing the phenomena of spontaneous symmetry breaking in gauge theories.Khosa, Charanjit KTue, 12 Jul 2016 06:14:51 GMThttp://ilcdoc.linearcollider.org/record/631012016SIMP from a strong U(1) gauge theory with a monopole condensation
http://ilcdoc.linearcollider.org/record/63100
We provide a variant model of strongly interacting massive particle (SIMP), where composite dark matter comes from a strongly interacting U(1) theory. We first explain a non-Abelian version of the model with an additional singlet field, which is mixed with the Higgs field to maintain the kinetic equilibrium between the hidden and Standard Model (SM) sectors. The mixing leads to signals that would be detected by future collider experiments, direct DM detection experiments, and beam-dump experiments. Then we investigate a U(1) theory with a scalar monopole, where U(1) charged particles are confined by monopole condensation. In this model, the radial component of monopole can mix with the Higgs field, so that we do not need to introduce the additional singlet field.Kamada, AyukiTue, 12 Jul 2016 06:14:50 GMThttp://ilcdoc.linearcollider.org/record/631002016Charged Lepton Flavour Violation and Neutrinoless Double Beta Decay in Left-Right Symmetric Models with Type I+II Seesaw
http://ilcdoc.linearcollider.org/record/63099
We study the new physics contributions to neutrinoless double beta decay ($0\nu\beta \beta$) half-life and lepton flavour violation (LFV) amplitude within the framework of the minimal left-right symmetric model (MLRSM). Considering all possible new physics contributions to $0\nu\beta \beta$ and charged lepton flavour violation $\mu \rightarrow e \gamma, \mu \rightarrow 3e$ in MLRSM, we constrain the parameter space of the model from the requirement of satisfying existing experimental bounds. Assuming the breaking scale of the left-right symmetry to be $\mathcal{O}(1)$ TeV accessible at ongoing and near future collider experiments, we consider the most general type I+II seesaw mechanism for the origin of tiny neutrino masses. Choosing the relative contribution of the type II seesaw term allows us to calculate the right handed neutrino mass matrix as well as Dirac neutrino mass matrix as a function of the model parameters, required for the calculation of $0\nu\beta \beta$ and LFV amplitudes. We show that such a general type I+II seesaw structure results in more allowed parameter space compared to individual type I or type II seesaw cases considered in earlier works. In particular, we show that the doubly charged scalar masses $M_{\Delta}$ are allowed to be smaller than the heaviest right handed neutrino mass $M_N$ from the present experimental bounds in these scenarios which is in contrast to earlier results with individual type I or type II seesaw showing $M_{\Delta} > M_N$.Borah, DebasishTue, 12 Jul 2016 06:14:50 GMThttp://ilcdoc.linearcollider.org/record/630992016Testing the dark matter scenario in the inert doublet model by future precision measurements of the Higgs boson couplings
http://ilcdoc.linearcollider.org/record/63098
We evaluate radiative corrections to the Higgs boson couplings in the inert doublet model, in which the lightest component of the $Z_2^{}$ odd scalar doublet field can be a dark matter candidate. The one-loop contributions to the $hVV$, $hff$ and $hhh$ couplings are calculated in the on-shell scheme, where $h$ is the Higgs boson with the mass 125 GeV, $V$ represents a weak gauge boson and $f$ is a fermion. We investigate how the one-loop corrected Higgs boson couplings can be deviated from the predictions in the standard model under the constraints from perturbative unitarity and vacuum stability in the scenario where the model can explain current dark matter data. When the mass of the dark matter is slightly above a half of the Higgs boson mass, it would be difficult to test the model by the direct search experiments for dark matter. We find that in such a case the model can be tested at future collider experiments by either the direct search of heavier inert particles or precision measurements of the Higgs boson couplings.Kanemura, ShinyaTue, 12 Jul 2016 06:14:50 GMThttp://ilcdoc.linearcollider.org/record/630982016Singlet-Catalyzed Electroweak Phase Transitions in the 100 TeV Frontier
http://ilcdoc.linearcollider.org/record/63097
We study the prospects for probing a gauge singlet scalar-driven strong first order electroweak phase transition with a future proton-proton collider in the 100 TeV range. Singlet-Higgs mixing enables resonantly-enhanced di-Higgs production, potentially aiding discovery prospects. We perform Monte Carlo scans of the parameter space to identify regions associated with a strong first-order electroweak phase transition, analyze the corresponding di-Higgs signal, and select a set of benchmark points that span the range of di-Higgs signal strengths. For the $b\bar{b}\gamma\gamma$ and $4\tau$ final states, we investigate discovery prospects for each benchmark point for the high luminosity phase of the Large Hadron Collider and for a future $pp$ collider with $\sqrt{s}$ = 50, 100, or 200 TeV. We find that any of these future collider scenarios could significantly extend the reach beyond that of the high luminosity LHC, and that with $\sqrt{s}$ = 100 TeV (200 TeV) and 30 ab$^{-1}$, the full region of parameter space favorable to strong first order electroweak phase transitions is almost fully (fully) discoverable.Kotwal, Ashutosh VTue, 12 Jul 2016 06:14:50 GMThttp://ilcdoc.linearcollider.org/record/630972016Near-threshold production of heavy quarks with QQbar_threshold
http://ilcdoc.linearcollider.org/record/63096
We describe the QQbar_threshold library for computing the production cross section of heavy quark-antiquark pairs near threshold at electron-positron colliders. The prediction includes all presently known QCD, electroweak, Higgs, and nonresonant corrections in the combined nonrelativistic and weak-coupling expansion.Beneke, MTue, 12 Jul 2016 06:14:50 GMThttp://ilcdoc.linearcollider.org/record/630962016Probing the origin of 750 GeV diphoton excess with the precision measurements at the ILC
http://ilcdoc.linearcollider.org/record/63095
The recently reported diphoton excess at the LHC may imply the existence of a new resonance with a mass of about 750 GeV which couples to photons via loops of new charged particles. In this letter, we study the possibility to test such models at the ILC, paying attention to the new charged particles responsible for the diphoton decay of the resonance. We show that they affect the scattering processes $e^+e^- \to f\bar{f}$ (with $f$ denoting Standard Model fermions) at the ILC, which makes it possible to indirectly probe the new charged particles even if they are out of the kinematical reach. We also show that the discriminations of the diphoton models may be possible based on a study of the angular distributions of $f\bar{f}$.Bae, Kyu JungTue, 12 Jul 2016 06:14:50 GMThttp://ilcdoc.linearcollider.org/record/630952016Electroweak radiative corrections to triple photon production at the ILC
http://ilcdoc.linearcollider.org/record/63094
In this paper, we present the precision predictions for three photon production in the standard model (SM) at the ILC including the full next-to-leading (NLO) electroweak (EW) corrections, high order initial state radiation (h.o.ISR) contributions and beamstrahlung effects. We present the LO and the NLO EW+h.o.ISR+beamstrahlung corrected total cross sections for various colliding energy when $\sqrt s \ge 200 {\rm GeV}$ and the kinematic distributions of final photons with $\sqrt s = 500 {\rm GeV}$ at ILC, and find that the NLO EW corrections, the h.o.ISR contributions and the beamstrahlung effects are important in exploring the process $e^+e^- \to \gamma\gamma\gamma$.Zhang, YuTue, 12 Jul 2016 06:14:50 GMThttp://ilcdoc.linearcollider.org/record/630942016Baryogenesis from leptomesons
http://ilcdoc.linearcollider.org/record/63093
Various new physics models, e.g., theories of compositeness, can accommodate the color singlet excited leptons that interact with the leptons, quarks, leptoquarks, etc. A particular type of excited lepton, which can be produced through the four-fermion interaction with lepton and quark-antiquark (or lepton-antilepton) pair, we call leptomeson. These new particles may contribute to variety of the experimental anomalies such as the discrepancy in the muon g-2. We propose that the leptomesons can generate also the baryon asymmetry that explains the imbalance in ordinary matter and antimatter in the observable universe. We consider the two types of scenarios for this baryogenesis via leptogenesis to occur from either leptomeson oscillations or decays. Both possibilities do not contradict to the small masses of the observable neutrinos and the proton stability. Moreover they can be relevant for the near future collider experiments and do not suffer from the gravitino problem.Zhuridov, DmitryTue, 12 Jul 2016 06:14:50 GMThttp://ilcdoc.linearcollider.org/record/630932016New Physics at the TeV Scale
http://ilcdoc.linearcollider.org/record/63092
The Standard Model of particle physics is assumed to be a low-energy effective theory with new physics theoretically motivated to be around TeV scale. The dissertation presents theories with new physics beyond the Standard Model at the TeV scale testable in the current High Energy Colliders. The study on leptoquarks gauge bosons in reference to TopSU(5) model in chapter 2 showed that their discovery mass range extends upto 1.5 TeV at 14 TeV LHC with luminosity of 100 $fb^{-1}$. On the other hand, in chapter 3 we studied the collider phenomenology of TeV scale mirror fermions in Left-Right Mirror model finding that the reaches for the mirror quarks goes upto $750$ GeV at the $14$ TeV LHC with $~300 ~fb^{-1}$ luminosity. In chapter 4 we have enlarged the bosonic symmetry to fermi-bose symmetry e.g. supersymmetry and have shown that SUSY with non-universalities in gaugino or scalar masses within high scale SUGRA set up can still be accessible at LHC with 14 TeV. In chapter 5, we performed a study in respect to the $e^+e^-$ collider and find that precise measurements of the higgs boson mass splittings upto $\sim 100$ MeV may be possible with high luminosity in the International Linear Collider (ILC). In chapter 6 we have shown that the experimental data on neutrino masses and mixings are consistent with the proposed 4/5 parameter Dirac neutrino models yielding a solution for the neutrino masses with inverted mass hierarchy and large CP violating phase $\delta$ and thus can be tested experimentally. Chapter 7 incorporates a warm dark matter candidate in context of two Higgs doublet model. The model has several testable consequences at LHC. This dissertation presents an endeavor to study beyond standard model (BSM) physics at the TeV scale with testable signals in the Colliders.Chakdar, ShreyashiTue, 12 Jul 2016 06:14:49 GMThttp://ilcdoc.linearcollider.org/record/630922016Mixed Dark Matter in Left-Right Symmetric Models
http://ilcdoc.linearcollider.org/record/63091
Motivated by the recently reported diboson and dijet excesses in Run 1 data at ATLAS and CMS, we explore models of mixed dark matter in left-right symmetric theories. In this study, we calculate the relic abundance and the elastic scattering cross section with nuclei for a number of dark matter candidates that appear within the fermionic multiplets of left-right symmetric models. In contrast to the case of pure multiplets, WIMP-nucleon scattering proceeds at tree-level, and hence the projected reach of future direct detection experiments such as LUX-ZEPLIN and XENON1T will cover large regions of parameter space for TeV-scale thermal dark matter. Decays of the heavy charged W' boson to particles in the dark sector can potentially shift the right-handed gauge coupling to larger values when fixed to the rate of the Run 1 excesses, moving towards the theoretically attractive scenario, gR = gL. This region of parameter space may be probed by future collider searches for new Higgs bosons or electroweak fermions.Berlin, AsherTue, 12 Jul 2016 06:14:49 GMThttp://ilcdoc.linearcollider.org/record/630912016The Higgs Portal and Cosmology
http://ilcdoc.linearcollider.org/record/63090
Higgs portal interactions provide a simple mechanism for addressing two open problems in cosmology: dark matter and the baryon asymmetry. In the latter instance, Higgs portal interactions may contain the ingredients for a strong first order electroweak phase transition as well as new CP-violating interactions as needed for electroweak baryogenesis. These interactions may also allow for a viable dark matter candidate. We survey the opportunities for probing the Higgs portal as it relates to these questions in cosmology at the LHC and possible future colliders.Assamagan, KeteviTue, 12 Jul 2016 06:14:49 GMThttp://ilcdoc.linearcollider.org/record/630902016Coherent Showers for the LHC
http://ilcdoc.linearcollider.org/record/63089
We present a full-fledged antenna shower for hadron collisions in the Vincia framework and focus on initial state radiation. The current version of the shower is limited to massless QCD partons and colourless resonances. As a proof-of-concept for the applicability of tree-level matrix-element corrections a la GKS we study $Z$ boson production at the LHC, corrected up to Born + $\mathcal{O}(\alpha_s^2)$, and show some first results with matrix-element corrections.Fischer, NadineTue, 12 Jul 2016 06:14:49 GMThttp://ilcdoc.linearcollider.org/record/630892016