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A low-energy solution to the mu-problem in gauge mediation
http://ilcdoc.linearcollider.org/record/63139
In the gauge-mediation framework the soft supersymmetry breaking mass parameters of the supersymmetric standard model are induced by the gauge interactions of some messenger fields. The parameters exhibit flavor universality which is dictated by the gauge interactions and which efficiently eliminates new dangerous contributions to flavor changing neutral currents. However, the Higgs potential in this framework typically contains an unacceptable hierarchy between its dimensionful parameters (the $\mu$-problem of gauge mediation). We show that the problem can be resolved if the Higgs potential arises dynamically once an intermediate U(1)' sector is integrated out rather than arising radiatively from some Yukawa interactions at the messenger scale. As an added benefit, such models may naturally avoid new contribution to CP violating amplitudes. The proposed framework is described, explicit examples are given and its phenomenology is explored. The $\mu$ problem is resolved in this case by the low-energy U(1)' dynamics which could be tested in future collider experiments.Langacker, PaulThu, 25 Aug 2016 18:33:08 GMThttp://ilcdoc.linearcollider.org/record/631392016The visible effect of a very heavy magnetic monopole at colliders
http://ilcdoc.linearcollider.org/record/63138
If a heavy Dirac monopole exists, the light-to-light scattering below the monopole production threshold is enhanced due to strong coupling of monopoles to photons. At the next Linear Collider with electron beam energy 250 GeV this photon pair production could be observable at monopole masses less than 2.5-6.4 TeV in the $e^+e^-$ mode or 3.7-10 TeV in the $\gamma\gamma$ mode, depending on the monopole spin. At the upgraded Tevatron such an effect is expected to be visible at monopole masses below 1-2.5 TeV. The strong dependence on the initial photon polarizations allows to find the monopole spin in experiments at $e^+e^-$ and $\gamma\gamma$ colliders. We consider the $Z\gamma$ production and the $3\gamma$ production at $e^+e^-$ and $pp$ or $p\bar{p}$ colliders via the same monopole loop. The possibility to discover these processes is significantly lower than that of the $\gamma\gamma$ case.Ginzburg, I FThu, 25 Aug 2016 18:33:08 GMThttp://ilcdoc.linearcollider.org/record/631382016More and More Indirect Signals for Extra Dimensions at More and and More Colliders
http://ilcdoc.linearcollider.org/record/63137
It has been recently suggested by Arkani-Hamed, Dimopoulos and Dvali that gravity may become strong at energies not far above the electroweak scale and thus remove the hierarchy problem. Such a scenario can be tested at both present and future accelerators since towers of Kaluza-Klein gravitons and associated scalar fields now play an important phenomenological role. In this paper we examine several processes for their sensitivity to a low scale for quantum gravity including deep inelastic $ep$ scattering at HERA, high precision low energy $\nu N$ scattering, Bhabha and Moller scattering at linear colliders and both fermion and gluon pair production at $\gamma \gamma$ colliders.Rizzo, Thomas GThu, 25 Aug 2016 18:33:08 GMThttp://ilcdoc.linearcollider.org/record/631372016Systematics of single superpartners production at leptonic colliders
http://ilcdoc.linearcollider.org/record/63136
We examine the effects of the lepton number violating R parity odd interactions, $\lambda_{ijk} $, on single production of fermion (charginos and neutralinos) and scalar (sleptons and sneutrinos) superpartners at leptonic colliders for center of mass energies up to $500GeV - 1TeV$. The probability amplitudes for all the five relevant $2 \to 2$ body processes and the decays branching ratios for the produced superpartners are calculated at tree level. A semi-quantitative discussion is developed within a supergravity model assuming grand unification of gauge interactions and universal (flavor independent) soft supersymmetry breaking parameters at the unification scale. The predictions obtained for the total and partial rates show that the single production reactions have a good potential of observability at NLC (Next Linear Colliders) energies. For values of the R parity violating coupling constant, $\lambda _{ijk}= 0.05$, close to the current bounds, the $\tilde \chi^{\pm, 0}$ reactions could probe all the relevant intervals for $\tan \beta$ and $m_0$ and broad regions of the parameter space for $\mu$ and $M_2$, while the $\tilde \nu $ and $\tilde l $ productions could probe sneutrinos and sleptons masses up to the kinematical limits. Using the hypothesis of a single dominant R parity violating coupling constant, a Monte Carlo events simulation for the $ \tilde \chi^{\pm, 0} $ reactions is employed to deduce some characteristic final states dynamical distributions.Chemtob, MarcThu, 25 Aug 2016 18:33:08 GMThttp://ilcdoc.linearcollider.org/record/631362016Optimal Spin Basis in Polarized Photon Linear Colliders
http://ilcdoc.linearcollider.org/record/63135
We analyze the spin correlations of the top quark pairs produced at Photon Linear Colliders. We employ the circular polarized photon beams and general spin basis for the top quark pair. We consider general spin bases to find a strong spin correlation between produced top quark and anti-top quark. We show the cross-section in these bases and discuss the characteristics of results.Hori, MichihiroThu, 25 Aug 2016 18:33:08 GMThttp://ilcdoc.linearcollider.org/record/631352016CP Violating Anomalous Couplings at a 500 GeV e+ e- Linear Collider
http://ilcdoc.linearcollider.org/record/63134
We study the sensitivity of a 500 GeV $e^+e^-$ Linear Collider to $CP$ violating anomalous couplings. We find that with 50~fb$^{-1}$, and taking only one non-zero coupling at a time, the process $e^+e^-\to W^+ W^-$ can be used to place the 95% confidence level bounds $|\tilde\kappa_\gamma|\leq0.1$, $|\tilde\kappa_Z|\leq 0.1$ and $|g_4^Z|\leq 0.1$ from CP even observables. By studying certain distributions in the process $e^+e^-\to \mu^+\mu^-\nu\bar{\nu}$ one of the bounds can be improved to $|g_4^Z| \leq 0.06$. This process also allows the construction of a CP odd observable which can be used to place bounds on CP violating new physics. At the 95% confidence level we find $|\tilde\kappa_\gamma|\leq 0.3$, $|\tilde\kappa_Z|\leq 0.2$ and a much weaker bound for $|g_4^Z|$.Likhoded, A AThu, 25 Aug 2016 18:33:08 GMThttp://ilcdoc.linearcollider.org/record/631342016Contributions of LEP1.5, LEP2 and linear-collider data to indirect constraints on non-Abelian gauge-boson couplings
http://ilcdoc.linearcollider.org/record/63133
It is possible to place direct constraints on WW-photon and WWZ couplings by studying their tree-level contributions to the process e^+e^- ---> W^+W^-. However, these couplings also contribute at the loop level to e^+e^- ---> f fbar processes where `f' is any Standard-Model fermion. In this paper the available LEP1.5 and LEP2 data, the anticipated LEP2 data and possible linear collider data for these latter processes is combined with low-energy and Z-pole data to place indirect constraints on nonstandard WW-photon and WWZ couplings. The direct and indirect constraints are then compared. An effective Lagrangian is used to describe the new physics. In order that the implications of this analysis are as broad as possible, both the light-Higgs scenario, described by an effective Lagrangian with a linear realization of the symmetry-breaking sector, and the strongly interacting scenario, described by the electroweak chiral Lagrangian, are considered.Szalapski, RThu, 25 Aug 2016 18:33:08 GMThttp://ilcdoc.linearcollider.org/record/631332016J/\psi Electromagnetic Production at e^+e^- colliders
http://ilcdoc.linearcollider.org/record/63132
Within the framework of QED we investigate the inclusive J/\psi production at $e^+e^-$ colliders. It is expected to be as a further test to the charmonium production mechanisms and QED. We find that at the energies of CESR, BEPC, and TRISTAN (e.g. 4.0 GeV \leq \sqrt s \leq 60 GeV), the contributions of the concerned electromagnetic processes to the $J/\psi$ inclusive production are great, even dominant, thus they greatly affect the observation of the color-octet $J/\psi$ production signature at $e^+e^-$ colliders. The production of \psi', being similar to that of J/\psi's, is roughly estimated, and its influence on the observation of the color-octet J/\psi production signature in e^+e^- collision is also discussed.Chang, Chao-HsiThu, 25 Aug 2016 18:33:08 GMThttp://ilcdoc.linearcollider.org/record/631322016An Exploration of Below Threshold $Z'$ Mass and Coupling Determinations at the NLC
http://ilcdoc.linearcollider.org/record/63131
We examine of the capability of the Next Linear Collider to determine the mass as well as the couplings to leptons and $b$-quarks of a new neutral gauge boson, $Z'$, below direct production threshold. By using simulated data collected at several different values of $\sqrt s$, we demonstrate how this can be done in a model-independent manner via an anonymously case approach. The importance of beam polarization to the success of this program is discussed. The procedure is shown to be easily extended to the case of top and charm quark couplings.Rizzo, Thomas GThu, 25 Aug 2016 18:33:08 GMThttp://ilcdoc.linearcollider.org/record/631312016Trilinear anomalous gauge couplings and non-standard fermionic couplings
http://ilcdoc.linearcollider.org/record/63130
In this paper we do an analysis of the reaction $e^+e^-\to W^+W^-$ for various options of the Next Linear Colliders (NLC), by considering the possibility of deviations from the Standard Model induced by anomalous trilinear vector boson couplings and non-standard fermionic couplings. We show that there are strong correlations among these parameters. By studying the high-energy behaviour of the helicity amplitudes we show that the error made in linearizing the cross-section in the anomalous and non-standard couplings increases with the square of the center of mass energy. We consider also the option of longitudinally polarized electron beams by showing that, in this case, the restrictions on the anomalous and non-standard parameters are greatly enhanced.Casalbuoni, RThu, 25 Aug 2016 18:33:08 GMThttp://ilcdoc.linearcollider.org/record/631302016Four-Fermi Effective Operators in Top-Quark Production and Decay
http://ilcdoc.linearcollider.org/record/63129
Effects of four-Fermi-type new interactions are studied in top-quark pair production and their subsequent decays at future e^+e^- colliders. Secondary-lepton-energy distributions are calculated for arbitrary longitudinal beam polarizations. An optimal-observables procedure is applied for the determination of new parameters.Grzadkowski, BThu, 25 Aug 2016 18:33:06 GMThttp://ilcdoc.linearcollider.org/record/631292016A wide scalar neutrino resonance and b\bar{b} production at LEP
http://ilcdoc.linearcollider.org/record/63128
In supersymmetric models with R-parity violation, scalar neutrinos may be produced as s-channel resonances in e^+e^- colliders. We note that within current constraints, the scalar neutrino may have a width of several GeV into b\bar{b} and be produced with large cross section, leading to a novel supersymmetry discovery signal at LEP II. In addition, if the scalar neutrino mass approximately equals m_Z, such a resonance necessarily increases R_b and reduces A_{FB}(b), significantly improving the fit to electroweak data. Bounds from B meson and top quark decays are leading constraints, and we stress the importance of future measurements.Erler, JensThu, 25 Aug 2016 18:33:06 GMThttp://ilcdoc.linearcollider.org/record/631282016The Conversion of CESR to Operate as the Test Accelerator, CesrTA, Part 4: Superconducting Wiggler Diagnostics
http://ilcdoc.linearcollider.org/record/63127
Cornell's electron/positron storage ring (CESR) was modified over a series of accelerator shutdowns beginning in May 2008, which substantially improves its capability for research and development for particle accelerators. CESR's energy span from 1.8 to 5.6 GeV with both electrons and positrons makes it appropriate for the study of a wide spectrum of accelerator physics issues and instrumentation related to present light sources and future lepton damping rings. Additionally a number of these are also relevant for the beam physics of proton accelerators. This paper, the last in a series of four, describes the vacuum system modifications of the superconducting wigglers to accommodate the diagnostic instrumentation for the study of electron cloud (EC) behavior within wigglers. Earlier papers provided an overview of the accelerator physics program, the general modifications of CESR, the modifications of the vacuum system necessary for the conversion of CESR to the test accelerator, CesrTA, enhanced to study such subjects as low emittance tuning methods, EC effects, intra-beam scattering, fast ion instabilities as well as general improvements to beam instrumentation. While the initial studies of CesrTA focussed on questions related to the International Linear Collider damping ring design, CESR is a very versatile storage ring, capable of studying a wide range of accelerator physics and instrumentation questions.Billing, M GWed, 24 Aug 2016 18:31:01 GMThttp://ilcdoc.linearcollider.org/record/631272016Measurement of the $\tau$ lepton polarization in the decay ${\bar B} \rightarrow D^* \tau^- {\bar \nu_{\tau}}$
http://ilcdoc.linearcollider.org/record/63126
We report the first measurement of the $\tau$ lepton polarization in the decay ${\bar B} \rightarrow D^* \tau^- {\bar\nu_{\tau}}$ as well as a new measurement of the ratio of the branching fractions $R(D^{*}) = \mathcal{B}({\bar B} \rightarrow D^* \tau^- {\bar\nu_{\tau}}) / \mathcal{B}({\bar B} \rightarrow D^* \ell^- {\bar\nu_{\ell}})$, where $\ell^-$ denotes an electron or a muon, with the decays $\tau^- \rightarrow \pi^- \nu_{\tau}$ and $\tau^- \rightarrow \rho^- \nu_{\tau}$. We use the full data sample of $772 \times 10^6$ $B{\bar B}$ pairs accumulated with the Belle detector at the KEKB electron-positron collider. Our preliminary results, $R(D^*) = 0.276 \pm 0.034{\rm (stat.)} ^{+0.029} _{-0.026}{\rm (syst.)}$ and $P_{\tau} = -0.44 \pm 0.47 {\rm (stat.)} ^{+0.20} _{-0.17} {\rm (syst.)}$, are consistent with the theoretical predictions of the Standard Model within $0.6$ standard deviation.Abdesselam, AWed, 24 Aug 2016 18:31:00 GMThttp://ilcdoc.linearcollider.org/record/631262016NLO QCD Corrections for $J/\psi+ c + \bar{c}$ Production in Photon-Photon Collision
http://ilcdoc.linearcollider.org/record/63125
The $\gamma+\gamma\rightarrow J/\psi+c+\bar{c}$ inclusive process is an extremely important subprocess in $J/\psi$ photoproduction, like at LEP\uppercase\expandafter{\romannumeral2} or various types future electron-positron colliders. In this work we perform the next-to-leading(NLO) QCD corrections to this process in the framework of non-relativistic QCD(NRQCD) factorization formalism, the first NLO calculation for two projectiles to 3-body quarkonium inclusive production process. By setting the center-of-mass energy at LEP\uppercase\expandafter{\romannumeral2}, the $\sqrt{s}=197$ GeV, we conduct analyses of the $p_t^2$ distribution and total cross section of this process at the NLO accuracy. It turns out that the total cross section is moderately enhanced by the NLO correction with a $K$ factor of about 1.46, and hence the discrepancy between DELPHI data and color-singlet(CS) calculation is reduced while the color-octet(CO) contributions are still inevitable at this order. At the future Circular Electron-Positron Collider(CEPC), the NLO corrections are found to be more significant, with a $K$ factor of about 1.76.Chen, Zi-QiangTue, 23 Aug 2016 18:29:18 GMThttp://ilcdoc.linearcollider.org/record/631252016Radiative Corrections to Chargino Production in Electron-Positron Collisions with Polarised Beams
http://ilcdoc.linearcollider.org/record/63124
We study radiative corrections to chargino production at linear colliders with polarised electron beams. We calculate the one-loop corrected cross-sections for polarised electon beams due to three families of quarks and squarks, working in the $\bar{MS}$ scheme, extending our previous calculation of the unpolarised cross-section with one-loop corrections due to the third family of quarks and squarks. In some cases we find rather large corrections to the tree-level cross-sections. For example for the case of right-handed polarised electrons and large $\tan \beta$ the corrections can be of order 30%, allowing sensitivity to the squark mass parameters.Díaz, Marco ATue, 16 Aug 2016 18:17:01 GMThttp://ilcdoc.linearcollider.org/record/631242016Discovery Limits for Extra Gauge Bosons in e^+e^- to \nu \bar{\nu} \gamma
http://ilcdoc.linearcollider.org/record/63123
We study the sensitivity of the process e^+ e^- \to \nu\bar{\nu}\gamma to extra gauge bosons, particularly W' bosons. Depending on the model, evidence for extra W bosons in this process can be detected for W' masses up to several TeV.Godfrey, StephenMon, 15 Aug 2016 18:15:05 GMThttp://ilcdoc.linearcollider.org/record/631232016Manifestations of Space-Time Multidimensionality in Scattering of Scalar Particles
http://ilcdoc.linearcollider.org/record/63122
We analyze a possibility of experimental detection of the contribution of the Kaluza-Klein tower of heavy particles to scattering cross-section in a six-dimensional scalar model with two dimensions being compactified to the torus with the radii $R$. It is shown that there is a noticeable effect even for the energies of colliding particles below $R^{-1}$ which may be observed in future collider experiments if $R^{-1}$ is of the order of $1 TeV$.Demichev, A PMon, 15 Aug 2016 18:15:00 GMThttp://ilcdoc.linearcollider.org/record/631222016SUSY Dark Matter in Universal and Nonuniversal Gaugino Mass Models
http://ilcdoc.linearcollider.org/record/63121
We review the phenomenology of SUSY dark matter in various versions of MSSM, with universal and nonuniversal gaugino masses at the GUT scale. We start with the universal case (CMSSM), where the cosmologically compatible dark matter relic density is achieved only over some narrow regions of parameter space, involving some fine-tuning. Moreover, most of these regions are seriously challenged by the constraints from collider and direct dark matter detection experiments. Then we consider some simple and predictive nonuniversal gaugino mass models, based on SU(5) GUT. Several of these models offer viable SUSY dark matter candidates, which are compatible with the cosmic dark matter relic density and the above mentioned experimental constraints. They can be probed at the present and future collider and dark matter search experiments. Finally, we consider the nonuniversal gaugino mass model arising from anomaly mediated SUSY breaking. In this case the cosmologically compatible dark matter relic density requires dark matter mass of a few TeV, which puts it beyond the scope of collider and direct dark matter detection experiments. However, it has interesting predictions for some indirect dark matter detection experiments.Roy, D PThu, 11 Aug 2016 18:07:50 GMThttp://ilcdoc.linearcollider.org/record/631212016Luminosity Limitations in Linear Colliders Based on Plasma Acceleration
http://ilcdoc.linearcollider.org/record/63120
Particle acceleration in plasma creates a possibility of exceptionally high accelerating gradients and appears as a very attractive option for future linear electron-positron and/or photon-photon colliders. These high accelerating gradients were already demonstrated in a number of experiments. However, a linear collider requires exceptionally high beam brightness which still needs to be demonstrated. In this article we discuss major phenomena which limit the beam brightness of accelerated beam and, consequently, the collider luminosity.Lebedev, ValeriTue, 09 Aug 2016 18:04:05 GMThttp://ilcdoc.linearcollider.org/record/631202016FCC Based Lepton-Hadron and Photon-Hadron Colliders: Luminosity and Physics
http://ilcdoc.linearcollider.org/record/63119
Construction of future electron-positron colliders (or dedicated electron linac) and muon colliders (or dedicated muon ring) tangential to Future Circular Collider (FCC) will give opportunity to utilize highest energy proton and nucleus beams for lepton-hadron and photon-hadron collisions. Luminosity values of FCC based ep, \mup, eA, \muA, \gammap and \gammaA colliders are estimated. Multi-TeV center of mass energy ep colliders based on the FCC and linear colliders (LC) are considered in detail. Parameters of upgraded versions of the FCC proton beam are determined to optimize luminosity of electron-proton collisions keeping beam-beam effects in mind. Numerical calculations are performed using a currently being developed collision point simulator. It is shown that L_{ep}\sim10^{32}\,cm^{-2}s^{-1} can be achieved with LHeC-like upgrade of the FCC parameters.Acar, Y CTue, 09 Aug 2016 18:04:04 GMThttp://ilcdoc.linearcollider.org/record/631192016Probing light-quark Yukawa couplings via hadronic event shapes at lepton colliders
http://ilcdoc.linearcollider.org/record/63118
We propose a novel idea for probing the Higgs boson couplings through the measurement of hadronic event shape distributions in the decay of the Higgs boson at lepton colliders. The method provides a unique test of the Higgs boson couplings and of QCD effects in the decay of the Higgs boson. It can be used to directly probe the Yukawa couplings of the light quarks and to further test the mechanism of electroweak symmetry breaking. From a case study for the proposed Circular Electron-Positron Collider, light-quark couplings with a strength greater than 8% of the bottom-quark Yukawa coupling in the standard model can be excluded.Gao, JunMon, 08 Aug 2016 18:02:08 GMThttp://ilcdoc.linearcollider.org/record/631182016Electroweak precision observables and Higgs-boson signal strengths in the Standard Model and beyond: present and future
http://ilcdoc.linearcollider.org/record/63117
We present results from a state-of-the-art fit of electroweak precision observables and Higgs-boson signal-strength measurements performed using 7 and 8 TeV data from the Large Hadron Collider. Based on the HEPfit package, our study updates the traditional fit of electroweak precision observables and extends it to include Higgs-boson measurements. As a result we obtain constraints on new physics corrections to both electroweak observables and Higgs-boson couplings. We present the projected accuracy of the fit taking into account the expected sensitivities at future colliders.de Blas, JorgeFri, 05 Aug 2016 17:57:09 GMThttp://ilcdoc.linearcollider.org/record/631172016The Light and Heavy Higgs Interpretation of the MSSM
http://ilcdoc.linearcollider.org/record/63116
We perform a parameter scan of the phenomenological Minimal Supersymmetric Standard Model (pMSSM) with eight parameters taking into account the experimental Higgs boson results from Run I of the LHC and further low-energy observables. We investigate various MSSM interpretations of the Higgs signal at 125 GeV. First, the light CP-even Higgs boson being the discovered particle. In this case it can impersonate the SM Higgs-like signal either in the decoupling limit, or in the limit of alignment without decoupling. In the latter case, the other states in the Higgs sector can also be light, offering good prospects for upcoming LHC searches and for searches at future colliders. Second, we demonstrate that the heavy CP-even Higgs boson is still a viable candidate to explain the Higgs signal - albeit only in a highly constrained parameter region, that will be probed by LHC searches for the CP-odd Higgs boson and the charged Higgs boson in the near future. As a guidance for such searches we provide new benchmark scenarios that can be employed to maximize the sensitivity of the experimental analysis to this interpretation.Bechtle, PhilipWed, 03 Aug 2016 17:53:14 GMThttp://ilcdoc.linearcollider.org/record/631162016Multiplicity distributions for $e^{+}e^{-}$ collisions using Weibull distribution
http://ilcdoc.linearcollider.org/record/63115
The two parameters Weibull function is used to describe the charged particle multiplicity distribution in $e^{+}e^{-}$ collisions at the highest available energy measured by TASSO and ALEPH experiments. The Weibull distribution has wide applications in naturally evolving processes based on fragmentation and sequential branching. The Weibull model describes the multiplicity distribution very well, as particle production processes involve QCD parton fragmentation. The effective energy model of particle production was verified using Weibull parameters and the same was used to predict the multiplicity distribution in $e^{+}e^{-}$ collisions at future collider energies.Dash, SadhanaMon, 01 Aug 2016 17:49:55 GMThttp://ilcdoc.linearcollider.org/record/631152016