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Flavour-changing Higgs decays into bottom and strange quarks in supersymmetry
http://ilcdoc.linearcollider.org/record/62091
In this work, we explore the flavour changing decays $H_i \to b s$ in a general supersymmetric scenario. In these models, the flavour changing decays arise at loop-level but, originating from a dimension-four operator, do not decouple and may provide a first sign of new physics for heavy masses beyond collider reach. In the framework of the minimal supersymmetric extension of the Standard Model (MSSM), we find that the largest branching ratio of the lightest Higgs ($H_1$) is ${\cal O}(10^{-6})$ after imposing present experimental constraints. While heavy Higgs states may still present branching ratios ${\cal O}(10^{-3})$. In a more general supersymmetric scenario, where additional Higgs states may modify the Higgs mixings, the branching ratio BR($H_1 \to b s$) can reach values ${\cal O}(10^{-4})$ , while heavy Higgses still remain at ${\cal O}(10^{-3})$. Although these values are clearly out of reach for the LHC, a full study in a linear collider environment could be worth.Barenboim, GFri, 31 Jul 2015 23:27:33 GMThttp://ilcdoc.linearcollider.org/record/620912015Photoproduction of Prompt $J/\psi$ in Association with a $c\bar{c}$ Pair within the Framework of Non-relativistic QCD at the International Linear Collider
http://ilcdoc.linearcollider.org/record/62090
We present a systematical study on the photoproduction of prompt $J/\psi$ in association with a $c\bar{c}$ pair within the framework of non-relativistic QCD at the future high-energy $e^{+}e^{-}$ collider - International Linear Collider, including both direct and feed-down contributions. For direct $J/\psi$ production, the states with color-octet $c\bar{c}$-components, especially $|c\bar{c}[^3P^{[8]}_J]g\rangle$ and $|c\bar{c}[^1S^{[8]}_0]g\rangle$, provide dominant contribution to the production cross-section, which are about sixty times over that of the color-singlet state $|c\bar{c}[^3S^{[1]}_1]\rangle$. This is clearly shown by the transverse momentum ($p_t$) and rapidity distributions. The feed-down contribution from $\psi'$ and $\chi_{cJ}$ ($J=0,1,2$) is sizable, which is $\sim 20\%$ to the total prompt cross-section. Besides the yields, we also calculate the $J/\psi$ polarization parameter $\lambda$. In small $p_t$ region, the polarization of the prompt $J/\psi$ is longitudinal due to $|c\bar{c}[^3P^{[8]}_J]g\rangle$, which becomes transverse in high $p_t$ region due to $|c\bar{c}[^3S^{[8]}_1]gg\rangle$. Thus the $J/\psi$ photoproduction shall provide a useful platform for testing the color-octet mechanism.Sun, ZhanThu, 30 Jul 2015 23:25:55 GMThttp://ilcdoc.linearcollider.org/record/620902015TID-Effect Compensation and Sensor-Circuit Cross-Talk Suppression in Double-SOI Devices
http://ilcdoc.linearcollider.org/record/62073
We are developing double silicon-on-insulator (DSOI) pixel sensors for various applications such as for high-energy experiments. The performance of DSOI devices has been evaluated including total ionization damage (TID) effect compensation in transistors using a test-element-group (TEG) up to 2 MGy and in integration-type sensors up to 100 kGy. In this article, successful TID compensation in a pixel-ASD-readout-circuit is shown up to 100 kGy for the application of DSOI to counting-type sensors. The cross-talk suppression in DSOI is being evaluated. These results encourage us that DSOI sensors are applicable to future high-energy experiments such as the BELLE-II experiment or the ILC experiment.Honda, ShunsukeTue, 28 Jul 2015 23:22:29 GMThttp://ilcdoc.linearcollider.org/record/620732015Single solenoidal magnetic system for Iron-free detector
http://ilcdoc.linearcollider.org/record/62066
We consider a single solenoidal system for possible usage in Iron-free detectors for future linear collidersMikhailichenko, AlexanderMon, 27 Jul 2015 23:20:48 GMThttp://ilcdoc.linearcollider.org/record/620662015Determining $V_{tb}$ at Electron-Positron Colliders
http://ilcdoc.linearcollider.org/record/62064
Verifying $V_{tb} \simeq 1$ is critical to test the three generation assumption of the Standard Model. So far our best knowledge of $V_{tb}$ is inferred either from the $3\times 3$ unitarity of CKM matrix or from single top-quark productions upon the assumption of universal weak couplings. The unitarity could be relaxed in new physics models with extra heavy quarks and the universality of weak couplings could also be broken if the $Wtb$ coupling is modified in new physics models. In this work we propose to measure $V_{tb}$ in the process of $e^+ e^- \to t\bar{t}$ without prior knowledge of the number of fermion generations or the strength of the $Wtb$ coupling. Using an effective Lagrangian approach, we perform a model-independent analysis of the interactions among electroweak gauge bosons and the third generation quarks, i.e. the $Wtb$, $Zt\bar{t}$ and $Zb\bar{b}$ couplings. The electroweak symmetry of the Standard Model specifies a pattern of deviations of the $Z$-$t_L$-$t_L$ and $W$-$t_L$-$b_L$ couplings after one imposes the known experimental constraint on the $Z$-$b_L$-$b_L$ coupling. We demonstrate that, making use of the predicted pattern and the accurate measurements of top-quark mass and width from the energy threshold scan experiments, one can determine $V_{tb}$ from the cross section and the forward-backward asymmetry of top-quark pair production at an {\it unpolarized} electron-positron collider.Cao, Qing-HongThu, 23 Jul 2015 23:14:06 GMThttp://ilcdoc.linearcollider.org/record/620642015Experimental Tests of Particle Flow Calorimetry
http://ilcdoc.linearcollider.org/record/62055
Precision physics at future colliders requires highly granular calorimeters to support the Particle Flow Approach for event reconstruction. This article presents a review of about 10 - 15 years of R\&D;, mainly conducted within the CALICE collaboration, for this novel type of detector. The performance of large scale prototypes in beam tests validate the technical concept of particle flow calorimeters. The comparison of test beam data with simulation, of e.g.\ hadronic showers, supports full detector studies and gives deeper insight into the structure of hadronic cascades than was possible previously.Sefkow, FelixWed, 22 Jul 2015 23:12:24 GMThttp://ilcdoc.linearcollider.org/record/620552015Characteristics of Non-Irradiated and Irradiated Double SOI Integration Type Sensor
http://ilcdoc.linearcollider.org/record/62052
We are developing monolithic pixel sensors based on a 0.2 $\mu$m fully-depleted Silicon-on-Insulator (SOI) technology for HEP experiment applications. The total ionizing dose (TID) effect is the major issue in the applications for hard radiation environments in HEP experiments. To compensate for TID damage, we have introduced a Double SOI structure which has a Middle Silicon layer (SOI2 layer) in addition. We studied the recovery from TID damage induced by $\mathrm{^{60}Co}~\gamma$'s and other characteristics of an Integration-type Double SOI sensor. The Double SOI sensor irradiated to 100 kGy showed a response for IR laser similar to of a non-irradiated sensor when we applied a negative voltage to the SOI2 layer. We conclude that the Double SOI sensor is radiation hard enough to be used in HEP experiments in harsh radiation environments such as at Bell II or ILC.Asano, MariTue, 21 Jul 2015 23:10:45 GMThttp://ilcdoc.linearcollider.org/record/620522015Physics potential for the measurement of ${\sigma(H\nu\bar{\nu})\times \text{BR}(H\rightarrow\mu^+\mu^-)}$ at the 1.4 TeV CLIC collider
http://ilcdoc.linearcollider.org/record/62035
The future Compact Linear Collider (CLIC) offers a possibility for a rich precision physics programme, in particular in the Higgs sector through the energy staging. This is the first paper addressing the measurement of the Standard Model Higgs boson decay into two muons at 1.4 TeV CLIC. With respect to similar studies at future linear colliders, this paper includes several novel contributions to the statistical uncertainty of the measurement. The later includes the Equivalent Photon Approximation and realistic forward electron tagging based on energy deposition maps in the forward calorimeters, as well as several processes with the Beamstrahlung photons that results in irreducible contribution to the signal. In addition, coincidence of the Bhabha scattering with the signal and background processes is considered, altering the signal selection efficiency. The study is performed using a fully simulated CLIC_ILD detector model. It is shown that the branching ratio for the Higgs decay into a pair of muons BR(${H\rightarrow\mu^+\mu^-}$) times the Higgs production cross-section in $WW$-fusion $\sigma(H\nu\bar{\nu})$ can be measured with 38% statistical accuracy at ${\sqrt{s} =\text{1.4 TeV}}$, assuming an integrated luminosity of 1.5 ab$^{-1}$ with unpolarised beams. If 80% electron beam polarisation is considered, the statistical uncertainty of the measurement is reduced to 25%. Systematic uncertainties are negligible in comparison to the statistical uncertainty.MilutinoviÄ‡-DumbeloviÄ‡, GFri, 17 Jul 2015 23:04:07 GMThttp://ilcdoc.linearcollider.org/record/620352015Type-III Seesaw fermionic triplets at the International Linear Collider
http://ilcdoc.linearcollider.org/record/62021
The signature of heavy fermionic triplets belonging to Type III seesaw at the International Linear Collider (ILC) is probed. Presence of charged fermionic triplets upto a mass of about $ 750$ GeV could be established through single production at a 1 TeV ILC with moderate luminosity of 300 fb$^{-1}$, assuming a fermion triplet-electron mixing of about 0.05. Unlike the case of LHC, the production process is highly sensitive to the mixing, making the process interesting. The single production of neutral triplet is found to be somewhat harder, considering the large SM background present. Pair production of triplets of mass 500 GeV considered at 2 TeV centre of mass energy presents convenient ways to study different mixing scenarios. The production process is sensitive to $V_e$. The pair production along with information regarding single production would be able to identify the mixing scenarios.Goswami, DeepanjaliThu, 16 Jul 2015 23:02:24 GMThttp://ilcdoc.linearcollider.org/record/620212015Radiative corrections to the Triple Higgs Coupling in the Inert Higgs Doublet Model
http://ilcdoc.linearcollider.org/record/62012
We investigate the implication of the recent discovery of a Higgs-like particle in the first phase of the LHC Run 1 on the Inert Higgs Doublet Model (IHDM). The determination of the Higgs couplings to SM particles and its intrinsic properties will get improved during the new LHC Run 2 starting this year. The new LHC Run 2 would also shade some light on the triple Higgs coupling. Such measurement is very important in order to establish the details of the electroweak symmetry breaking mechanism. Given the importance of the Higgs couplings both at the LHC and $e^+e^-$ Linear Collider machines, accurate theoretical predictions are required. We study the radiative corrections to the triple Higgs coupling $hhh$ and to $hZZ$, $hWW$ couplings in the context of the IHDM. By combining several theoretical and experimental constraints on parameter space, we show that extra particles might modify the triple Higgs coupling near threshold regions. Finally, we discuss the effect of these corrections on the double Higgs production signal at the $e^+e^-$ LC and show that they can be rather important.Arhrib, AbdesslamWed, 15 Jul 2015 23:00:43 GMThttp://ilcdoc.linearcollider.org/record/620122015Vector resonances in weak-boson-fusion at future pp colliders
http://ilcdoc.linearcollider.org/record/62011
We present a first estimate of the reach of future pp colliders, the 14 TeV LHC and a futuristic 100 TeV pp collider, on a vector resonance, specifically a $W^{'}$, produced via weak-boson-fusion, and decaying dominantly into $tb$. The analysis is motivated by Composite Higgs, Randall-Sundrum and Little Higgs scenarios, which predict the existence of vector resonances with a large coupling to $W$ and $Z$ longitudinal bosons. In particular, in composite Higgs models with partial compositeness, the standard Drell-Yan production channel is suppressed at large coupling while the weak-boson-fusion is enhanced and could thus provide a unique opportunity to directly test the large coupling regime of the theory. We outline a search strategy for the $W^{'}$ in the weak-boson-fusion channel and present the reach of future colliders on the $W^{'}$ mass-coupling parameter space.Mohan, KirtimaanWed, 15 Jul 2015 23:00:42 GMThttp://ilcdoc.linearcollider.org/record/620112015Charged Higgs Study through Triple or Double Higgs Production in a General Two Higgs Doublet Model at Future Lepton Collide
http://ilcdoc.linearcollider.org/record/62005
In this study the charged Higgs signal through triple or double Higgs production in a general two Higgs doublet model (2HDM) is investigated. The main production process is $e^+e^- \rightarrow H^+H^-H^0$ followed by the charged Higgs decay to a pair of $\tau \nu$ and the neutral Higgs decay to $b\bar{b}$. The alternative process $H^+W^-H^0$ is also included as a source of charged Higgs signal in the analysis having comparable cross-section. The focus is on a future $e^+e^-$ linear collider operating at $\sqrt{s}=1.5$ TeV. The final state under consideration ($\tau^+ \tau^- b \bar{b} E^{\textnormal{miss}}_{T}$) is suitable for electroweak background rejection using the $b-$tagging tools. It is shown that although the signal cross section is small, with a reasonable background suppression, high signal significance values are achievable at an integrated luminosity $500 fb^{-1}$ depending on the charged Higgs mass, $\tan\beta~$ and the CP-odd neutral Higgs mass. Finally results are quoted in terms of the signal significance for charged Higgs in the mass range $170<m_{H^{\pm}}<400$ GeV.Ahmed, IjazTue, 14 Jul 2015 22:59:00 GMThttp://ilcdoc.linearcollider.org/record/620052015Beam Dump Experiment at Future Electron-Positron Colliders
http://ilcdoc.linearcollider.org/record/61999
We propose a new beam dump experiment at future colliders with electron ($e^-$) and positron ($e^+$) beams, BDee, which will provide a new possibility to search for hidden particles, like hidden photon. If a particle detector is installed behind the beam dump, it can detect the signal of in-flight decay of the hidden particles produced by the scatterings of $e^\pm$ beams off materials for dumping. We show that, compared to past experiments, BDee (in particular BDee at $e^+e^-$ linear collider) significantly enlarges the parameter region where the signal of the hidden particle can be discovered.Kanemura, ShinyaMon, 13 Jul 2015 22:57:14 GMThttp://ilcdoc.linearcollider.org/record/619992015Prospects for Triple Gauge Coupling Measurements at the 14 TeV LHC and Future Lepton Colliders
http://ilcdoc.linearcollider.org/record/61989
The $WW$ production is the primary channel to directly probe the triple gauge couplings. We first analyze the $e^+ e^- \rightarrow W^+ W^-$ process at the future lepton collider, China's proposed Circular Electron-Positron Collider (CEPC). We use the five kinematical angles in this process to constrain the anomalous triple gauge couplings and relevant Dimension six operators at the CEPC up to the order of $10^{-4}$. The most sensible information is obtained from the distributions of the production scattering angle and the decay azimuthal angles. We also estimate constraints at the 14 TeV LHC, with both 300 fb$^{-1}$ and 3000 fb$^{-1}$ integrated luminosity from the leading lepton $p_T$ and azimuthal angle difference $\Delta \phi_{ll}$ distributions in the di-lepton channel. The constrain is somewhat weaker, up to the order of $10^{-3}$. The limits on the triple gauge couplings are complementary to those on the electroweak precision observables and higgs couplings. Our results show that the sensitivity gap between electroweak and triple gauge boson precision can be significantly improved to less than one order at the 14 TeV LHC and both can be further improved at the CEPC.Bian, LigongThu, 09 Jul 2015 22:50:26 GMThttp://ilcdoc.linearcollider.org/record/619892015Direct detection of singlet dark matter in classically scale-invariant standard model
http://ilcdoc.linearcollider.org/record/61970
Classical scale invariance is one of the possible solutions to explain the origin of the electroweak scale. The simplest extension is the classically scale-invariant standard model augmented by a multiplet of gauge singlet real scalar. In the previous study it was shown that the properties of the Higgs potential deviates substantially, which can be observed in the International Linear Collider. On the other hand, since the multiplet does not acquire vacuum expectation value, the singlet components are stable and can be dark matter. In this letter we study the detectability of the real singlet scalar bosons in the experiment of the direct detection of dark matter. It is shown that a part of this model has already been excluded and the rest of the parameter space is within the reach of the future experiment.Endo, KazuhiroWed, 08 Jul 2015 22:48:41 GMThttp://ilcdoc.linearcollider.org/record/619702015Near-threshold production of $W^\pm$, $Z^0$ and $H^0$ at a fixed-target experiment at the future ultra-high-energy proton colliders
http://ilcdoc.linearcollider.org/record/61962
We outline the opportunities to study the production of the Standard Model bosons, $W^\pm$, $Z^0$ and $H^0$ at "low" energies at fixed-target experiments based at possible future ultra-high-energy proton colliders, \ie\ the High-Energy LHC, the Super proton-proton Collider and the Future Circular Collider -- hadron-hadron. These can be indeed made in conjunction with the proposed future colliders designed to reach up to $\sqrt{s}=100$ TeV by using bent crystals to extract part of the halo of the beam which would then impinge on a fixed target. Without disturbing the collider operation, this technique allows for the extraction of a substantial amount of particles in addition to serve for a beam-cleaning purpose. With this method, high-luminosity fixed-target studies at centre-of-mass energies above the $W^\pm$, $Z^0$ and $H^0$ masses, $\sqrt{s} \simeq 170-300$ GeV, are possible. We also discuss the possibility offered by an internal gas target, which can also be used as luminosity monitor by studying the beam transverse shape.Lansberg, J PTue, 07 Jul 2015 22:46:55 GMThttp://ilcdoc.linearcollider.org/record/619622015Reduced LHC constraints for higgsino-like heavier electroweakinos
http://ilcdoc.linearcollider.org/record/61961
As a sequel to our earlier work on wino-dominated $\tilde \chi_1^{\pm}$ and $\tilde \chi_2^{0}$ (wino models), we focus on pMSSM models where $\tilde \chi_1^{\pm}$ and $\tilde \chi_{2,3}^{0}$ are either higgsino dominated (higgsino models) or admixtures of significant amount of higgsino and wino components (mixed models), with or without light sleptons. The LHC constraints in the trilepton channel are significantly weaker even in the presence of light sleptons, especially in the higgsino models, compared to those mostly studied by the LHC collaborations with wino-dominated $\tilde \chi_1^{\pm}$ and $\tilde \chi_2^{0}$. The modes $\tilde \chi_{2,3}^{0}\rightarrow h~\tilde\chi_1^{0}$ with large branching ratios (BRs) are more common in the higgsino models and may produce spectacular signal in the LHC Run-II. In a variety of higgsino and mixed models we have delineated the allowed parameter space due to the LHC constraints, the observed Dark Matter (DM) relic density of the universe, which gets contributions from many novel DM producing mechanisms i.e., the annihilation/coannhilation processes that lead to the correct range of relic density, and the precise measurement of the anomalous magnetic moment of the muon. In the higgsino models many new DM producing mechanisms, which are not allowed in the wino models, open up. We have also explored the prospects of direct and indirect detection of DM in the context of LUX and IceCube experiments respectively. In an extended model having only light gluinos in addition to the electroweak sparticles, the gluinos decay into final states with multiple taggable b-jets with very large BRs. As a consequence, the existing ATLAS data in the $0l$ + jets (3b) + $E\!\!\!\!/_T$ channel provide the best limit on $m_{\tilde g}$ ($\approx$ 1.3 TeV). Several novel signatures of higgsino models for LHC Run-II and ILC have been identified.Chakraborti, ManimalaTue, 07 Jul 2015 22:46:55 GMThttp://ilcdoc.linearcollider.org/record/619612015Renormalization Group Constraints on New Top Interactions from Electroweak Precision Data
http://ilcdoc.linearcollider.org/record/61944
Anomalous interactions involving the top quark contribute to some of the most difficult observables to directly access experimentally. They can give however a sizeable correction to very precisely measured observables at the loop level. Using a model-independent effective Lagrangian approach, we present the leading indirect constraints on dimension-six effective operators involving the top quark from electroweak precision data. They represent the most stringent constraints on these interactions, some of which may be directly testable in future colliders.de Blas, JorgeMon, 06 Jul 2015 22:45:12 GMThttp://ilcdoc.linearcollider.org/record/619442015Anomalous $WW\gamma$ couplings with beam polarization at the Compact Linear Collider
http://ilcdoc.linearcollider.org/record/61870
We study the anomalous $WW\gamma$ couplings at the Compact Linear Collider through the processes $e^{+}e^{-}\to W^+W^-$, $e^{-}e^{+} \to e^{-} \gamma^{*} e^{+} \to e^{+} \nu_{e} W^-$ and $e^{-}e^{+}\to e^{-} \gamma^{*} \gamma^{*} e^{+} \to e^{-} W^+ W^- e^{+} $ $ (\gamma^{*}$ is the Weizsacker-Williams photon). We give the 95\% confidence level limits for unpolarized and polarized electron (positron) beam on the anomalous couplings for various values of the integrated luminosities and center-of-mass energies. We show that the obtained limits on the anomalous couplings through these processes can highly improve the current experimental limits. In addition, our limits with beam polarization are approximately two times better than the unpolarized case.ArÄ±, VWed, 01 Jul 2015 22:36:46 GMThttp://ilcdoc.linearcollider.org/record/618702015Discriminating between SUSY and Non-SUSY Higgs Sectors through the Ratio $H \to b \bar b / H \to \tau^+ \tau^-$ with a 125 GeV Higgs boson
http://ilcdoc.linearcollider.org/record/61868
It is still an open question whether the new scalar particle discovered at the LHC with a mass of 125 GeV is the SM Higgs boson or it belongs to models of new physics with an extended Higgs sector, as the MSSM or 2HDM. The ratio of branching fractions $R$ = BR($H \to b \bar b$)/BR($H \to \tau^+ \tau^-$) of Higgs boson decays is a powerful tool in order to distinguish the MSSM Higgs sector from the SM or non-supersymmetric 2HDM. This ratio receives large renormalization-scheme independent radiative corrections in supersymmetric models at large $\tan\beta$, which are insensitive to the SUSY mass scale and absent in the SM or 2HDM. Making use of the current LHC data and the upcoming new results on Higgs couplings to be reported by ATLAS and CMS collaborations and in a future linear collider, we develop a detailed and updated study of this ratio $R$ which improves previous analyses and sets the level of accuracy needed to discriminate between models.Arganda, ETue, 30 Jun 2015 22:35:04 GMThttp://ilcdoc.linearcollider.org/record/618682015Extending the Matrix Element Method beyond the Born approximation: Calculating event weights at next-to-leading order accuracy
http://ilcdoc.linearcollider.org/record/61867
In this article we illustrate how event weights for jet events can be calculated efficiently at next-to-leading order (NLO) accuracy in QCD. This is a crucial prerequisite for the application of the Matrix Element Method in NLO. We modify the recombination procedure used in jet algorithms, to allow a factorisation of the phase space for the real corrections into resolved and unresolved regions. Using an appropriate infrared regulator the latter can be integrated numerically. As illustration, we reproduce differential distributions at NLO for two sample processes. As further application and proof of concept, we apply the Matrix Element Method in NLO accuracy to the mass determination of top quarks produced in e+e- annihilation. This analysis is relevant for a future Linear Collider. We observe a significant shift in the extracted mass depending on whether the Matrix Element Method is used in leading or next-to-leading order.Martini, TillTue, 30 Jun 2015 22:35:03 GMThttp://ilcdoc.linearcollider.org/record/618672015LCFIPlus: A Framework for Jet Analysis in Linear Collider Studies
http://ilcdoc.linearcollider.org/record/61866
We report on the progress in flavor identification tools developed for a future $e^+e^-$ linear collider such as the International Linear Collider (ILC) and Compact Linear Collider (CLIC). Building on the work carried out by the LCFIVertex collaboration, we employ new strategies in vertex finding and jet finding, and introduce new discriminating variables for jet flavor identification. We present the performance of the new algorithms in the conditions simulated using a detector concept designed for the ILC. The algorithms have been successfully used in ILC physics simulation studies, such as those presented in the ILC Technical Design Report.Suehara, TaikanTue, 30 Jun 2015 22:35:03 GMThttp://ilcdoc.linearcollider.org/record/618662015Gravitational mass of relativistic matter and antimatter
http://ilcdoc.linearcollider.org/record/61856
The universality of free fall, the weak equivalence principle (WEP), is a cornerstone of the general theory of relativity, the most precise theory of gravity confirmed in all experiments up to date. The WEP states the equivalence of the inertial, $m$, and gravitational, $m_g$, masses and was tested in numerous occasions with normal matter at relatively low energies. However, there is no proof for the matter and antimatter at high energies. For the antimatter the situation is even less clear -- current direct observations of trapped antihydrogen suggest the limits $-65 < m_g / m < 110$ not excluding the so-called antigravity phenomenon, i.e. repulsion of the antimatter by Earth. Here we demonstrate an indirect bound $0.96 < m_g/m < 1.04$ on the gravitational mass of relativistic electrons and positrons coming from the absence of the vacuum Cherenkov radiation at the Large Electron-Positron Collider (LEP) and stability of photons at the Tevatron collider in presence of the annual variations of the solar gravitational potential. Our result clearly rules out the speculated antigravity. By considering the absolute potential of the Local Supercluster (LS), we also predict the bounds $1 - 4\times 10^{-7} < m_g/m < 1 + 2\times 10^{-7}$ for an electron and positron. Finally, we comment on a possibility of performing complementary tests at the future International Linear Collider (ILC) and Compact Linear Collider (CLIC).Kalaydzhyan, TigranMon, 29 Jun 2015 22:33:20 GMThttp://ilcdoc.linearcollider.org/record/618562015$Z'$ resonance and associated $Zh$ production at future Higgs boson factory: ILC and CLIC
http://ilcdoc.linearcollider.org/record/61853
We study the prospects of the B-L model with an additional $Z'$ boson to be a Higgs boson factory at high-energy and high-luminosity linear electron positron colliders, such as the ILC and CLIC, through the Higgs-strahlung process $e^{+}e^{-}\rightarrow (Z, Z') \to Zh$, including both the resonant and non-resonant effects. We evaluate the total cross section of $Zh$ and we calculate the total number of events for integrated luminosities of 500-2000\hspace{0.8mm}$fb^{-1}$ and center of mass energies between 500 and 3000\hspace{0.8mm}$GeV$. We find that the total number of expected $Zh$ events can reach $10^6$, which is a very optimistic scenario and it would be possible to perform precision measurements for both the $Z'$ and Higgs boson in future high-energy $e^+e^-$ colliders experiments.Gutierrez-Rodriguez, AFri, 26 Jun 2015 22:28:20 GMThttp://ilcdoc.linearcollider.org/record/618532015Freeze-In Dark Matter with Displaced Signatures at Colliders
http://ilcdoc.linearcollider.org/record/61852
Dark matter, $X$, may be generated by new physics at the TeV scale during an early matter-dominated (MD) era that ends at temperature $T_R \ll {\rm TeV}$. Compared to the conventional radiation-dominated (RD) results, yields from both Freeze-Out and Freeze-In processes are greatly suppressed by dilution from entropy production, making Freeze-Out less plausible while allowing successful Freeze-In with a much larger coupling strength. Freeze-In is typically dominated by the decay of a particle $B$ of the thermal bath, $B \rightarrow X$. For a large fraction of the relevant cosmological parameter space, the decay rate required to produce the observed dark matter abundance leads to displaced signals at LHC and future colliders, for any $m_X$ in the range ${\rm keV} < m_X < m_B$ and for values of $m_B$ accessible to these colliders. This result applies whether the early MD era arises after conventional inflation, when $T_R$ is the usual reheat temperature, or is a generic MD era with an alternative origin. In the former case, if $m_X$ is sufficiently large to be measured from kinematics, the reheat temperature $T_R$ can be extracted. Our result is independent of the particular particle physics implementation of $B \rightarrow X$, and can occur via any operator of dimension less than 8 (4) for a post-inflation (general MD) cosmology. An interesting example is provided by DFS axion theories with TeV-scale supersymmetry and axino dark matter of mass GeV to TeV, which is typically overproduced in a conventional RD cosmology. If $B$ is the higgsino, $\tilde h$, Higgs, W and Z particles appear at the displaced decays, $\tilde h \rightarrow h \tilde a, Z \tilde a$ and $\tilde h^\pm \rightarrow W^\pm \tilde a$. The scale of axion physics, $f$, is predicted to be in the range $(3\times10^8 - 10^{12})$ GeV and, over much of this range, can be extracted from the decay length.Co, Raymond TFri, 26 Jun 2015 22:28:20 GMThttp://ilcdoc.linearcollider.org/record/618522015