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Single and double production of the Higgs boson at hadron and lepton colliders in minimal composite Higgs models
http://ilcdoc.linearcollider.org/record/63050
In the composite Higgs models, originally proposed by Georgi and Kaplan, the Higgs boson is a pseudo Nambu-Goldstone boson (pNGB) of spontaneous breaking of a global symmetry. In the minimal version of such models, global SO(5) symmetry is spontaneously broken to SO(4), and the pNGBs form an isospin doublet field, which corresponds to the Higgs doublet in the Standard Model (SM). Predicted coupling constants of the Higgs boson can in general deviate from the SM predictions, depending on the compositeness parameter. The deviation pattern is determined also by the detail of the matter sector. We comprehensively study how the model can be tested via measuring single and double production processes of the Higgs boson at LHC and future electron-positron colliders. The possibility to distinguish the matter sector among the minimal composite Higgs models is also discussed. In addition, we point out differences in the cross section of double Higgs boson production from the prediction in other new physics models.Kanemura, ShinyaFri, 18 Mar 2016 15:45:17 GMThttp://ilcdoc.linearcollider.org/record/630502016Search for Higgs portal DM at the ILC
http://ilcdoc.linearcollider.org/record/63049
Higgs portal dark matter (DM) models are simple interesting and viable DM models. There are three types of the models depending on the DM spin: scalar, fermion and vector DM models. In this paper, we consider renormalizable, unitary and gauge invariant Higgs portal DM models, and study how large parameter regions can be surveyed at the International Linear Collider (ILC) experiment at $\sqrt{s}=500$ GeV. For the Higgs portal singlet fermion and vector DM cases, the force mediator involves two scalar propagators, the SM-like Higgs boson and the dark Higgs boson. We show that their interference generates interesting and important patterns in the mono-$Z$ plus missing $E_T$ signatures at the ILC, and the results are completely different from those obtained from the Higgs portal DM models within the effective field theories. In addition, we show that it would be possible to distinguish the spin of DM in the Higgs portal scenarios, if the shape of the recoil-mass distribution is observed. We emphasize that the interplay between these collider observations and those in the direct detection experiments has to be performed in the model with renomalizability and unitarity to combine the model analyses in different scales.Ko, PWed, 16 Mar 2016 15:41:47 GMThttp://ilcdoc.linearcollider.org/record/630492016A First Look at the Impact of NNNLO Theory Uncertainties on Top Mass Measurements at the ILC
http://ilcdoc.linearcollider.org/record/63048
A scan of the top production threshold at a future electron-positron collider provides the possibility for a precise measurement of the top quark mass in theoretically well-defined mass schemes. With statistical uncertainties of 20 MeV or below, systematics will likely dominate the total uncertainty of the measurement. This contribution presents a first look at the impact of the renormalization scale uncertainties in recent NNNLO calculations of the top pair production cross section in the threshold region on the measurement of the top quark mass at the International Linear Collider.Simon, FrankWed, 16 Mar 2016 15:41:45 GMThttp://ilcdoc.linearcollider.org/record/630482016Higgs decay to two muons at ILC
http://ilcdoc.linearcollider.org/record/63047
The coupling of the Higgs to second generation particles can be studied by measuring the decay of the Higgs boson to two muons. In this analysis we considered the process at a centre of mass energy of 1 TeV, where the WW-fusion process is dominant and the Higgsstrahlung can be neglected. We assumed an integrated luminosity of 500 fb-1 and a beam polarization of (Pe- Pe+) = (-0.8,+0.2). We estimated the sensitivity of the Higgs coupling to muons using full simulation of the ILD detector described in the DBD. We developed a new selection for the two muons based on the latest available particle ID tools. This improved the sensitivity by more than 10%. A further 10% gains was achieved by exploiting multi variate techniques. Combining the two improvements we reached a sensitivity of 2.7, a significant improvement with respect to the previous estimate.Giannelli, Michele FaucciWed, 16 Mar 2016 15:41:44 GMThttp://ilcdoc.linearcollider.org/record/630472016Probe of the anomalous quartic $WWWW$ couplings with beam polarization at the CLIC
http://ilcdoc.linearcollider.org/record/63046
We have investigated the anomalous quartic $WWWW$ couplings defined by the dimension-8 operators in semi-leptonic decay channel of the $e^{+}e^{-}\rightarrow \nu_{e} W^{-} W^{+} \bar{\nu}_{e}$ process for unpolarized and polarized electron (positron) beam at the Compact Linear Collider. We give the $95\%$ confidence level bounds on anomalous $\frac{f_{S0}}{\Lambda^{4}}$, $\frac{f_{S1}}{\Lambda^{4}}$ and $\frac{f_{T0}}{\Lambda^{4}}$ couplings for various values of the integrated luminosities and center-of-mass energies. The best sensitivities obtained on anomalous $\frac{f_{S0}}{\Lambda^{4}}$, $\frac{f_{S1}}{\Lambda^{4}}$ and $\frac{f_{T0}}{\Lambda^{4}}$ couplings through the process $e^{+}e^{-}\rightarrow \nu_{e} W^{-} W^{+} \bar{\nu}_{e}$ with beam polarization at $\sqrt{s}=3$ TeV and an integrated luminosity of $L_{int}=2000$ fb$^{-1}$ are $[-4.05;\, 3.67]\times 10^{-12}$ GeV$^{-4}$, $[-3.08; \, 2.12]\times 10^{-12}$ GeV$^{-4}$, $[-1.98; \, 0.64]\times 10^{-13}$ GeV$^{-4}$, which show improvement over the current bounds.Senol, ATue, 15 Mar 2016 15:42:00 GMThttp://ilcdoc.linearcollider.org/record/630462016Dark matter relic density from observations of supersymmetry at the ILC
http://ilcdoc.linearcollider.org/record/63045
Supersymmetry can explain the observed dark matter relic density with a neutralino dark matter particle and a coannihilating, almost mass-degenerate sparticle. If this were the case in nature, a linear electron positron collider like the ILC could discover the two sparticles if their masses are in the kinematic reach of the collider. This contribution discusses which observations are necessary at the ILC for predicting the dark matter relic density correctly and for confirming that the observed lightest neutralino is the only kind of dark matter. We take the case of stau coannihilation as an example.Lehtinen, Suvi-LeenaTue, 15 Mar 2016 15:41:59 GMThttp://ilcdoc.linearcollider.org/record/630452016Neutral Higgs Boson Production at e^+e^- Colliders in the Complex MSSM: Towards the LC Precision
http://ilcdoc.linearcollider.org/record/63044
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 a precise knowledge of their production properties is mandatory. We review the evaluation of the cross sections for the neutral 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 mechanisms e^+e^- -> h_i Z, h_i gamma, h_i h_j (i,j = 1,2,3), 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 10-20% of the tree-level results, but can go up to 50% or higher.Heinemeyer, STue, 15 Mar 2016 15:41:59 GMThttp://ilcdoc.linearcollider.org/record/630442016SUSY Fits and their Implications for ILC and CLIC
http://ilcdoc.linearcollider.org/record/63043
We review results from our frequentist analysis of the parameter space of the pMSSM10, in which the following 10 soft SUSY-breaking parameters are specified independently at the mean scalar top mass scale Msusy = \sqrt{M_stop1 M_stop2}: the gaugino masses M_{1,2,3}, the 1st-and 2nd-generation squark masses M_squ1 = M_squ2, the third-generation squark mass M_squ3, a common slepton mass M_slep and a common trilinear mixing parameter A, the Higgs mixing parameter mu, the pseudoscalar Higgs mass M_A and tan beta, the ratio of the two Higgs vacuum expectation values. We implemented the LHC searches for strongly- and electroweakly-interacting sparticles and light stops, so as to confront the pMSSM10 parameter space with all relevant SUSY searches. In addition, our analysis includes Higgs mass and rate measurements, SUSY Higgs exclusion bounds, the measurements of \bmm, other B-physics observables, electroweak precision observables, the cold dark matter density and the searches for spin-independent dark matter scattering, assuming that the cold dark matter is mainly provided by the lightest neutralino. We discuss the discovery potential of future e^+e^- linear colliders, such as ILC and CLIC, in the preferred pMSSM10 parameter space.Heinemeyer, STue, 15 Mar 2016 15:41:59 GMThttp://ilcdoc.linearcollider.org/record/630432016Generalized focus point and mass spectra comparison of highly natural SUGRA GUT models
http://ilcdoc.linearcollider.org/record/63042
Supergravity grand unified models (SUGRA GUTs) are highly motivated and allow for a high degree of electroweak naturalness when the superpotential parameter mu~ 100-300 GeV (preferring values closer to 100 GeV). We first illustrate that models with radiatively-driven naturalness enjoy a generalized focus-point behavior wherein all soft terms are correlated instead of just scalar masses. Next, we generate spectra from four SUGRA GUT archetypes: 1. SO(10) models where the Higgs doublets live in different 10-dimensional irreducible representations (irreps), 2. models based on SO(10) where the Higgs multiplets live in a single 10-dimensional irrep but with D-term scalar mass splitting, 3. models based on SU(5) and 4. a more general SUGRA model with 12 independent parameters. Electroweak naturalness implies for all models a spectrum of light higgsinos with m(higgsinos)< 300 GeV and gluinos with m(gluino)< 2-4 TeV. However, masses and mixing in the third generation sfermion sector differ distinctly between the models. These latter differences would be most easily tested at a linear e^+e^- collider with \sqrt{s}~ multi-TeV-scale but measurements at a 50-100 TeV hadron collider are also possible.Baer, HowardTue, 15 Mar 2016 15:41:59 GMThttp://ilcdoc.linearcollider.org/record/630422016Automation of NLO processes and decays and POWHEG matching in WHIZARD
http://ilcdoc.linearcollider.org/record/63041
We give a status report on the automation of next-to-leading order processes within the Monte Carlo event generator WHIZARD, using GoSam and OpenLoops as provider for one-loop matrix elements. To deal with divergences, WHIZARD uses automated FKS subtraction, and the phase space for singular regions is generated automatically. NLO examples for both scattering and decay processes with a focus on e+e- processes are shown. Also, first NLO-studies of observables for collisions of polarized leptons beams, e.g. at the ILC, will be presented. Furthermore, the automatic matching of the fixed-order NLO amplitudes with emissions from the parton shower within the POWHEG formalism inside WHIZARD will be discussed. We also present results for top pairs at threshold in lepton collisions, including matching between a resummed threshold calculation and fixed-order NLO. This allows the investigation of more exclusive differential observables.Reuter, JTue, 15 Mar 2016 15:41:58 GMThttp://ilcdoc.linearcollider.org/record/630412016Transverse-momentum resummation of colorless final states at the NNLL+NNLO
http://ilcdoc.linearcollider.org/record/63040
We present a general framework that allows to compute the resummed transverse-momentum distribution of a system of colorless particles. The implementation is fully differential in the degrees of freedom of the final-state system. As a first application, we consider the transverse-momentum spectrum of ZZ and WW boson pairs produced in hadron collisions, where we resum the logarithmically enhanced contributions due to multiple soft-gluon emission at small transverse momenta to all orders in perturbation theory. We exploit the most advanced perturbative information for the ZZ and WW production processes that is available at present by combining next-to-next-to-leading order QCD corrections with next-to-next-to-leading logarithmic resummation.Wiesemann, MariusTue, 15 Mar 2016 15:41:58 GMThttp://ilcdoc.linearcollider.org/record/630402016Implications of recent progress in heavy-quark hadroproduction
http://ilcdoc.linearcollider.org/record/63039
We discuss recent theoretical progress in heavy-quark hadro-production, in particular focusing on processes involving charm-quarks, and on their implications in different fields of particle phenomenology, from collider to astroparticle physics.Garzelli, M VTue, 15 Mar 2016 15:41:57 GMThttp://ilcdoc.linearcollider.org/record/630392016Di-Higgs Decay of Stoponium at Future Photon-Photon Collider
http://ilcdoc.linearcollider.org/record/63038
We study the detectability of the stoponium in the di-Higgs decay mode at the photon-photon collider option of the International $e^+e^-$ Linear Collider (ILC), whose center-of-mass energy is planned to reach $\sim 1$ TeV. We find that $5\sigma$ detection of the di-Higgs decay mode is possible with the integrated electron-beam luminosity of $1 {\rm ab}^{-1}$ if the signal cross section, $\sigma(\gamma \gamma \rightarrow \sigma_{\tilde{t}_1} \rightarrow hh)$, of ${\cal O}(0.1)$ fb is realized for the stoponium mass smaller than $\sim$ 800 GeV at 1 TeV ILC. Such a value of the cross section can be realized in the minimal supersymmetric standard model (MSSM) with relatively large trilinear stop-stop-Higgs coupling constant. Implication of the stoponium cross section measurement for the MSSM stop sector is also discussed.Ito, HayatoTue, 15 Mar 2016 15:41:57 GMThttp://ilcdoc.linearcollider.org/record/630382016Hadronic contributions to electroweak observables in the framework of DPT
http://ilcdoc.linearcollider.org/record/63037
The hadronic contributions to the muon anomalous magnetic moment and to the shift of the electromagnetic fine structure constant at the scale of Z boson mass are evaluated within dispersively improved perturbation theory (DPT). The latter merges the corresponding perturbative input with intrinsically nonperturbative constraints, which originate in the respective kinematic restrictions. The obtained results conform with recent assessments of the quantities on hand.Nesterenko, A VTue, 15 Mar 2016 15:41:57 GMThttp://ilcdoc.linearcollider.org/record/630372016Lightness of Higgs Boson and Spontaneous CP-violation in the Lee Model: An Alternative Scenario
http://ilcdoc.linearcollider.org/record/63036
Based on the weakly-coupled two-Higgs-doublet model with spontaneous CP-violation (named Lee model) and the mechanism to generate the correlation between smallness of CP-violation and lightness of scalar mass, as we proposed earlier, we predicted a light CP-mixing scalar $\eta$ in which pseudoscalar component is dominant. It is a natural scenario in which $m_{\eta}\sim\mathcal{O}(10\textrm{GeV})\ll v$. Masses of all other scalars ($h$, $H$, $H^\pm$) should be around the electro-weak scale $v$. Among them, the 125 GeV Higgs ($h$) couplings are standard-model like, and the charged Higgs ($H^\pm$) mass should be around the heaviest neutral scalar ($H$) mass. We discussed all experimental constraints and showed that this scenario is still allowed by data. The strictest constraints come from the experiments of the flavor-changing processes and the EDM of lepton and neutron. We also discussed the future tests for this scenario. It is possible to discover the extra scalars or exclude this scenario at future colliders, especially at the LHC and $e^+e^-$ colliders with $\mathcal{O}(\textrm{ab}^{-1})$ luminosity. We also pointed out that the $Z$-mediated Higgs pair production via $e^+e^-\rightarrow h_ih_j$ ($h_i, h_j$ stand for two of the $\eta, h, H$) would be the key observable to confirm or exclude CP-violation in Higgs sector. The sensitivity to test this scenario is worth further studying in more details.Mao, Ying-nanTue, 15 Mar 2016 15:41:57 GMThttp://ilcdoc.linearcollider.org/record/630362016Probing top quark neutral couplings in the Standard Model Effective Field Theory at NLO QCD
http://ilcdoc.linearcollider.org/record/63035
Top quark pair production in association with a $Z$-boson or a photon at the LHC directly probes neutral top-quark couplings. We present predictions for these two processes in the Standard Model (SM) Effective Field Theory (EFT) at next-to-leading (NLO) order in QCD. We include the full set of CP-even dimension-six operators that enter the top-quark interactions with the SM gauge bosons. For comparison, we also present predictions in the SMEFT for top loop-induced $HZ$ production at the LHC and for $t\bar{t}$ production at the ILC at NLO in QCD. Results for total cross sections and differential distributions are obtained and uncertainties coming from missing higher orders in the strong coupling and in the EFT expansions are discussed. NLO results matched to the parton shower are available, allowing for event generation to be directly employed in an experimental analyses. Our framework provides a solid basis for the interpretation of current and future measurements in the SMEFT, with improved accuracy and precision.Bylund, Olga BessidskaiaTue, 15 Mar 2016 15:41:57 GMThttp://ilcdoc.linearcollider.org/record/630352016NLO calculations matched with the Nagy-Soper parton shower
http://ilcdoc.linearcollider.org/record/63034
An MC@NLO-like matching of NLO QCD calculations with the Nagy-Soper parton shower is briefly summarised. Uncertainties and ambiguities of the matching scheme are shortly discussed. A few results for the pp -> ttj + X production process at the LHC with sqrt(s) = 8 TeV are also shown. All results have been obtained using the Nagy-Soper parton shower implementation in the DEDUCTOR program together with the HELAC-NLO framework.Czakon, MichalTue, 15 Mar 2016 15:41:57 GMThttp://ilcdoc.linearcollider.org/record/630342016Wgamma and Zgamma production at the LHC in NNLO QCD
http://ilcdoc.linearcollider.org/record/63033
We consider the production of Wgamma and Zgamma pairs at the LHC, and report on the fully differential computation of next-to-next-to-leading order (NNLO) corrections in QCD perturbation theory. The calculation includes leptonic vector-boson decays with the corresponding spin correlations, off-shell effects and final-state photon radiation. We present numerical results for pp collisions at 7 TeV, and compare them with available ATLAS data. In the case of Zgamma production, the impact of NNLO corrections is generally moderate, ranging from 8% to 17%, depending on the applied cuts. In the case of Wgamma production, the NNLO effects are more important, and range from 19% to 26%, thereby improving the agreement of the theoretical predictions with the data. As expected, a veto against jets significantly reduces the impact of QCD radiative corrections.Grazzini, MassimilianoTue, 15 Mar 2016 15:41:57 GMThttp://ilcdoc.linearcollider.org/record/630332016Radiative neutrino mass generation from WIMP dark matter
http://ilcdoc.linearcollider.org/record/63032
The minimal seesaw extension of the Standard Model requires two electroweak singlet fermions in order to accommodate the neutrino oscillation parameters at tree level. Here we consider a next to minimal extension where light neutrino masses are generated radiatively by two electroweak fermions: one singlet and one triplet under SU(2). These should be odd under a parity symmetry and their mixing gives rise to a stable weakly interactive massive particle dark matter candidate. For mass in the GeV-TeV range, it reproduces the correct relic density, and provides an observable signal in nuclear recoil direct detection experiments. The fermion triplet component of the dark matter has gauge interactions, making it potentially detectable at present and near future collider experiments.Lineros, Roberto ATue, 15 Mar 2016 15:41:56 GMThttp://ilcdoc.linearcollider.org/record/630322016Effects of Sfermion Mixing induced by RGE in the CMSSM
http://ilcdoc.linearcollider.org/record/63031
Even within the Constrained Minimal Supersymmetric Standard Model (CMSSM) it is possible to induce sfermion flavor mixing through the Renormalization Group Equations (RGE) when the full structure of the Yukawa couplings is considered. We analyse the impact of including those effects on the accurate computation of $B$-physics observables, electroweak precision observables (EWPO) and the Higgs boson mass predictions.Gómez, Mario ETue, 15 Mar 2016 15:41:56 GMThttp://ilcdoc.linearcollider.org/record/630312016Design of Pre-Dumping Ring Spin Rotator with a Possibility of Helicity Switching for Polarized Positrons at the ILC
http://ilcdoc.linearcollider.org/record/63030
The use of polarized beams enhance the possibility of the precision measurements at the International Linear Collider (ILC). In order to preserve the degree of polarization during beam transport spin rotators are included in the current TDR ILC Lattice. In this report some advantages of using a combined spin rotator/spin flipper are discussed. A few possible lattice designs of spin flipper developed at DESY in 2012 are presented.Malysheva, L ITue, 15 Mar 2016 15:41:52 GMThttp://ilcdoc.linearcollider.org/record/630302016Updated Results of a Solid-State Sensor Irradiation Study for ILC Extreme Forward Calorimetry
http://ilcdoc.linearcollider.org/record/63029
Detectors proposed for the International Linear Collider (ILC) incorporate a tungsten sampling calorimeter (`BeamCal') intended to reconstruct showers of electrons, positrons and photons that emerge from the interaction point of the collider with angles between 5 and 50 milliradians. For the innermost radius of this calorimeter, radiation doses at shower max are expected to reach 100 Mrad per year, primarily due to minimum-ionizing electrons and positrons that arise in the induced electromagnetic showers of e+e- `beamstrahlung' pairs produced in the ILC beam-beam interaction. However, radiation damage to calorimeter sensors may be dominated by hadrons induced by nuclear interactions of shower photons, which are much more likely to contribute to the non-ionizing energy loss that has been observed to damage sensors exposed to hadronic radiation. We report here on the results of SLAC Experiment T-506, for which several different types of silicon diode and gallium-arsenide sensors were exposed to doses of radiation induced by showering electrons of energy 3.5-13.3 GeV. By embedding the sensor under irradiation within a tungsten radiator, the exposure incorporated hadronic species that would potentially contribute to the degradation of a sensor mounted in a precision sampling calorimeter. Depending on sensor technology, efficient charge collection was observed for doses as large as 270 Mrad.Courcoubetis, GeorgeTue, 15 Mar 2016 15:41:52 GMThttp://ilcdoc.linearcollider.org/record/630292016A coordinate description of partonic processes
http://ilcdoc.linearcollider.org/record/63028
We review a perturbative description of amplitudes in coordinate space, aiming at an intuitive perspective on the roles of "long" and "short" distances. We begin with coordinate-space leading regions for fixed-angle scattering amplitudes, and develop approximations and factorizations in analogy to similar procedures in momentum space. There are also applications to products of Wilson lines, including the familiar cusp amplitude. We briefly discuss cross sections from the coordinate viewpoint, and the mechanism by which infrared singularities cancel in inclusive cross sections.Erdogan, OzanTue, 15 Mar 2016 15:41:47 GMThttp://ilcdoc.linearcollider.org/record/630282016Generalised unitarity for dimensionally regulated amplitudes within FDF
http://ilcdoc.linearcollider.org/record/63027
We review the Four-Dimensional-Formulation variant of the Four-Dimensional-Helicity scheme, by showing two applications of this regularisation scheme. The first one is the computation of one-loop helicity amplitudes, for which we present preliminary results for the analytic expressions of the one-loop Higgs plus five- gluon amplitudes. In the second part, we study the Colour-Kinematics duality for off-shell diagrams in gauge theories coupled to matter, showing in a diagrammatic way that the Jacobi relations for the kinematic numerators of off-shell diagrams, built with Feynman rules in axial gauge, reduce to definite set of violating terms due to the contributions of sub-graphs only.Bobadilla, William J TorresTue, 15 Mar 2016 15:41:47 GMThttp://ilcdoc.linearcollider.org/record/630272016TeV scale mirage mediation in NMSSM and precision Higgs measurement
http://ilcdoc.linearcollider.org/record/63026
We propose that the TeV scale mirage mediation in the Next-to-Minimal Supersymmetric Standard Model (NMSSM) is a novel solution for the little hierarchy problem in supersymmetry. The 125 GeV Higgs boson can be accommodated with the new quartic coupling or the mixing with the singlet. The fine-tuning measures are estimated numerically and found as low as 10\% or below for $1.5$ TeV gluino and $1$ TeV stop. The higgsino can be as heavy as 500 GeV without deteriorating the fine-tuning. An undesirable singlet-doublet mixing in the Higgs sector is suppressed due to approximate scale symmetries. We investigate the couplings of the Higgs bosons and discuss the prospects for studying them at LHC and ILC.Okumura, Ken-ichiTue, 15 Mar 2016 15:41:46 GMThttp://ilcdoc.linearcollider.org/record/630262016