R. Godbole - CHEP, IISc, India

R. Godbole
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R. Godbole
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CHEP, IISc, India
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High Energy Physics - Phenomenology (48)
 
High Energy Physics - Experiment (20)
 
Physics - Accelerator Physics (2)
 
Cosmology and Nongalactic Astrophysics (1)
 
Physics - Instrumentation and Detectors (1)
 
Nuclear Theory (1)
 
High Energy Physics - Theory (1)
 
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Publications Authored By R. Godbole

In this set of four lectures I will discuss some aspects of the Standard Model (SM) as a quantum field theory and related phenomenological observations which have played a crucial role in establishing the $SU(2)_{L} \times U(1)_{Y}$ gauge theory as the correct description of Electro-Weak (EW) interactions. I will first describe in brief the idea of EW unification as well as basic aspects of the Higgs mechanism of spontaneous symmetry breaking. After this I will discuss anomaly cancellation, custodial symmetry and implications of the high energy behavior of scattering amplitudes for the particle spectrum of the EW theory. Read More

We study the decay of 125 GeV Higgs boson to light LSP neutralino in the phenomenological minimal supersymmetric standard model in the context of collider searches and astrophysical experiments. We consider the parameter space for light neutralinos that can be probed via the invisible Higgs decays and higgsino searches at the ILC. We consider the cases where the light neutralino is compatible with the observed relic density or where the thermal relic is over-abundant, pointing to non-standard cosmology. Read More

We present predictions of transverse single spin asymmetry (TSSA) in $p+p^\uparrow \rightarrow J/\psi+X$ using the color evaporation model of charmonium production in a generalized parton model (GPM) framework. For this purpose, we have used best fit parameters for the gluon Sivers function (GSF) extracted from PHENIX data on TSSA in $p+p^\uparrow \to \pi^0+X$ at midrapidity. We calculate asymmetry at $\sqrt{s}$ = 115 GeV, 200 GeV and 500 GeV and compare the results at 200 GeV with PHENIX data on TSSA in the process $p + p^\uparrow \to J/\psi+X$. Read More

In most of the models beyond the Standard Model, the top quark is expected to be polarized when produced in the decay of some heavier particle, like the gluino or the stop. The polarization is constructed, in an experiment or in simulations, through the distribution of top decay products. Here, we propose an estimator of top quark polarization that depends only on the kinematics of it's mother particle, apart from its decay couplings to top quarks, and is given in terms of the top polarization expected in the rest frame of the decaying particle. Read More

Heavy flavour production like $J/\psi$ and $D$- meson production in scattering of electrons/unpolarized protons off polarized proton target offer promising probes to investigate gluon Sivers function. In this talk, I will summarize our recent work on trasverse single spin asymmetry in $J/\psi $ -production and $D$ - meson production in $p p^\uparrow$ scattering using a generalized parton model approach. We compare predictions obtained using different models of gluon Sivers function within this approach and then, taking into account the transverse momentum dependent evolution of the unpolarized parton distribution functions and gluon Sivers function, we study the effect of evolution on asymmetry. Read More

We discuss the prospects for observing CP violation in the MSSM with six CP-violating phases, using a geometric approach to maximise CP-violating observables subject to the experimental upper bounds on electric dipole moments. We consider constraints from Higgs physics, flavour physics, the dark matter relic density and spin-independent scattering cross section with matter. Read More

We present expected values of the Single Spin Asymmetry (SSA) in $D$-meson production in the process $p+p^\uparrow \rightarrow D^0 + X $ at RHIC energy $(\sqrt{s}=200\text{ GeV})$ using a generalized parton model approach. We use fits to the gluon Sivers function obtained recently by D'Alesio {\it et al.,} by fitting to the asymmetry data for the process $p+p^\uparrow \rightarrow \pi^0+ X$ measured by the PHENIX collaboration at RHIC. Read More

A gluphilic scalar dark matter (GSDM) model has recently been proposed as an interesting vision for WIMP dark matter communicating dominantly with the Standard Model via gluons. We discuss the collider signature of a hard jet recoiling against missing momentum ("mono-jet") in such a construction, whose leading contribution is at one-loop. We compare the full one-loop computation with an effective field theory (EFT) treatment, and find (as expected) that EFT does not accurately describe regions of parameter space where mass of the colored mediator particles are comparable to the experimental cuts on the missing energy. Read More

If the recent indications of a possible state $\Phi$ with mass $\sim 750$ GeV decaying into two photons reported by ATLAS and CMS in LHC collisions at 13 TeV were to become confirmed, the prospects for future collider physics at the LHC and beyond would be affected radically, as we explore in this paper. Even minimal scenarios for the $\Phi$ resonance and its $\gamma \gamma$ decays require additional particles with masses $\gtrsim \frac12 m_\Phi$. We consider here two benchmark scenarios that exemplify the range of possibilities: one in which $\Phi$ is a singlet scalar or pseudoscalar boson whose production and $\gamma \gamma$ decays are due to loops of coloured and charged fermions, and another benchmark scenario in which $\Phi$ is a superposition of (nearly) degenerate CP-even and CP-odd Higgs bosons in a (possibly supersymmetric) two-Higgs doublet model also with additional fermions to account for the $\gamma \gamma$ decay rate. Read More

We explore beyond Standard Model (bSM) physics signatures in the $l+jets$ channel of $t\overline{t}$ pair production process at the Tevatron and the LHC. We study the effects of bSM physics scenarios on the top quark polarization and on the kinematics of the decay leptons. To this end, we construct asymmetries using the lepton energy and angular distributions. Read More

We consider a simple renormalizable model providing a UV completion for dark matter whose interactions with the Standard Model are primarily via the gluons. The model consists of scalar dark matter interacting with scalar colored mediator particles. A novel feature is the fact that (in contrast to more typical models containing dark matter whose interactions are mediated via colored scalars) the colored scalars typically decay into multi-quark final states, with no associated missing energy. Read More

The discovery of a Higgs boson with a mass of 126 GeV at the LHC when combined with the non-observation of new physics both in direct and indirect searches imposes strong constraints on supersymmetric models and in particular on the top squark sector. The experiments for direct detection of dark matter have provided with yet more constraints on the neutralino LSP mass and its interactions. After imposing limits from the Higgs, flavour and dark matter sectors, we examine the feasibility for a light stop in the context of the pMSSM, in light of current results for stop and other SUSY searches at the LHC. Read More

In this paper we consider the issue of the Froissart bound on the high energy behaviour of total cross sections. This bound, originally derived using principles of analyticity of scattering amplitudes, is seen to be satisfied by all the available experimental data on total hadronic cross sections. At strong coupling, gauge/gravity duality has been used to provide some insights into this behaviour. Read More

We investigate methods to explore the CP nature of the $ t\bar{t}h $ coupling at the LHC, focusing on associated production of the Higgs with a $t \bar{t}$ pair. We first discuss the constraints implied by low-energy observables and by the Higgs-rate information from available LHC data, emphasizing that they cannot provide conclusive evidence on the nature of this coupling. We then investigate kinematic observables that could probe the $ t\bar{t}h $ coupling directly, in particular quantities that can be constructed out of just lab-frame kinematics. Read More

We present estimates of Single Spin Asymmetry (SSA) in the electroproduction of $J/\psi$ taking into account the transverse momentum dependent (TMD) evolution of the gluon Sivers function and using Color Evaporation Model of charmonium production. We estimate SSA for JLab, HERMES, COMPASS and eRHIC energies using recent parameters for the quark Sivers functions which are fitted using an evolution kernel in which the perturbative part is resummed up to next-to-leading logarithms (NLL) accuracy. We find that these SSAs are much smaller as compared to our first estimates obtained using DGLAP evolution but are comparable to our estimates obtained using TMD evolution where we had used approximate analytical solution of the TMD evolution equation for the purpose. Read More

We estimate Sivers asymmetry in low virtuality photoproduction of $J/\psi$ using color evaporation model and taking into account $Q^2$- evolution of transverse momentum dependent PDF's and Sivers function. There is a substantial reduction in asymmetry as compared to our previous analysis wherein the $Q^2$-dependance came only from DGLAP evolution of collinear part of TMDs. The estimates of asymmetry are comparable to our earlier estimates in which we had used analytical solution of only an approximated form of the evolution equations. Read More

We explore the prospects for observing CP violation in the minimal supersymmetric extension of the Standard Model (MSSM) with six CP-violating parameters, three gaugino mass phases and three phases in trilinear soft supersymmetry-breaking parameters, using the CPsuperH code combined with a geometric approach to maximize CP-violating observables subject to the experimental upper bounds on electric dipole moments. We also implement CP-conserving constraints from Higgs physics, flavour physics and the upper limits on the cosmological dark matter density and spin-independent scattering. We study possible values of observables within the constrained MSSM (CMSSM), the non-universal Higgs model (NUHM), the CPX scenario and a variant of the phenomenological MSSM (pMSSM). Read More

We analyse the hVV (V = W, Z) vertex in a model independent way using Vh production. To that end, we consider possible corrections to the Standard Model Higgs Lagrangian, in the form of higher dimensional operators which parametrise the effects of new physics. In our analysis, we pay special attention to linear observables that can be used to probe CP violation in the same. Read More

We present estimates of Single Spin Asymmetry(SSA) in the electroproduction of J/{\psi} taking into account the transverse momentum dependent(TMD) evolution of the Sivers function. We estimate SSA for JLab, HERMES, COMPASS and eRHIC energies using color evaporation model of J/{\psi}. We have calculated the asymmetry using recent parameters extracted by Echevarria et al. Read More

We present the activities of the "New Physics" working group for the "Physics at TeV Colliders" workshop (Les Houches, France, 3--21 June, 2013). Our report includes new computational tool developments, studies of the implications of the Higgs boson discovery on new physics, important signatures for searches for natural new physics at the LHC, new studies of flavour aspects of new physics, and assessments of the interplay between direct dark matter searches and the LHC. Read More

Kinematical distributions of decay products of the top quark carry information on the polarisation of the top as well as on any possible new physics in the decay of the top quark. We construct observables in the form of asymmetries in the kinematical distributions to probe their effects. Charged-lepton angular distributions in the decay are insensitive to anomalous couplings to leading order. Read More

With the renewed interest in vector-like fermion extensions of the Standard Model, we present here a study of multiple vector-like theories and their phenomenological implications. Our focus is mostly on minimal flavor conserving theories that couple the vector-like fermions to the SM gauge fields and mix only weakly with SM fermions so as to avoid flavor problems. We present calculations for precision electroweak and vector-like state decays, which are needed to investigate compatibility with currently known data. Read More

We revisit the constraints on the parameter space of the Minimal Supersymmetric Standard Model (MSSM), from charge and color breaking minima in the light of information on the Higgs from the LHC so far. We study the behavior of the scalar potential keeping two light sfermion fields along with the Higgs in the pMSSM framework and analyze the stability of the vacuum. We find that for lightest stop $\lesssim 1$ TeV and small $\mu \lesssim 500$ GeV, the absolute stability of the potential can be attained only for $|X_{t}| \lesssim \sqrt{ 6 m_{\tilde{t}_1} m_{\tilde{t}_2}}$. Read More

We estimate transverse spin single spin asymmetry(TSSA) in the process $e+p^\uparrow \to J/\psi +X$ using color evaporation model of charmonium production. We take into account transverse momentum dependent(TMD) evolution of Sivers function and parton distribution function and show that the there is a reduction in the asymmetry as compared to our earlier estimates wherein the $Q^2$ - evolution was implemented only through DGLAP evolution of unpolarized gluon densities. Read More

The Large Hadron Collider(LHC) has completed its run at 8 TeV with the experiments ATLAS and CMS having collected about 25 $\rm fb^{-1}$ of data each. Discovery of a light Higgs boson, coupled with lack of evidence for supersymmetry at the LHC so far, has motivated studies of supersymmetry in the context of naturalness with the principal focus being the third generation squarks. In this work, we analyze the prospects of the flavor violating decay mode $\rm \tilde{t}_1\to c\chi_{1}^{0}$ at 8 and 13 TeV center of mass energy at the LHC. Read More

Light neutralino dark matter can be achieved in the Minimal Supersymmetric Standard Model if staus are rather light, with mass around 100 GeV. We perform a detailed analysis of the relevant supersymmetric parameter space, including also the possibility of light selectons and smuons, and of light higgsino- or wino-like charginos. In addition to the latest limits from direct and indirect detection of dark matter, ATLAS and CMS constraints on electroweak-inos and on sleptons are taken into account using a "simplified models" framework. Read More

We put forth conclusions and suggestions regarding the presentation of the LHC Higgs results that may help to maximize their impact and their utility to the whole High Energy Physics community. Read More

We consider ZH and WH production at the Large Hadron Collider, where the Higgs decays to a bb pair. We use jet substructure techniques to reconstruct the Higgs boson and construct angular observables involving leptonic decay products of the vector bosons. These efficiently discriminate between the tensor structure of the HVV vertex expected in the Standard Model and that arising from possible new physics, as quantified by higher dimensional operators. Read More

We argue that known systematics of hadron cross sections may cause different particles to freeze out of the fireball produced in heavy-ion collisions at different times. We find that a simple model with two freezeout points is a better description of data than that with a single freezeout, while still remaining predictive. The resulting fits seem to present constraints on the late stage evolution of the fireball, including the tantalizing possibility that the QCD chiral transition influences the yields at sqrt(S)=2700 GeV and the QCD critical point those at sqrt(S)=17. Read More

We perform a comprehensive analysis of the polarization of the top quarks originating from sbottom-pair production at the LHC, followed by sbottom decays to top+chargino. We study moreover the expected net polarization of top quarks produced in sbottom-to-chargino and stop-to-neutralino decays in scenarios with small chargino - neutralino mass difference, where these decays may be hard to distinguish. We show that, in contrast to top quarks produced via the Standard Model processes, the average polarization of top quarks originating from these SUSY decays can obtain any value between +1 and -1. Read More

We extend our analysis of transverse single spin asymmetry (SSA) in electroproduction of $J/\psi$ to include the effect of the scale evolution of the transverse momentum dependent (TMD) parton distribution functions and gluon Sivers function. We estimate SSA for JLab, HERMES, COMPASS, and eRHIC energies using the color evaporation model of charmonium production, using an analytically obtained approximate solution of TMD evolution equations discussed in the literature. We find that there is a reduction in the asymmetry compared with our predictions for the earlier case considered by us, wherein the $Q^2$ dependence came only from DGLAP evolution of the unpolarized gluon densities and a different parametrization of the TMD Sivers function was used. Read More

We summarise a recent study looking at top quark polarisation effects in charged Higgs boson production. Lab frame angular and energy observables relating to leptonic decays of top quarks are analysed, and corresponding asymmetry parameters obtained. These are shown to be sensitive to top polarisation and robust with respect to higher order corrections. Read More

Determining the spin and the parity quantum numbers of the recently discovered Higgs-like boson at the LHC is a matter of great importance. In this paper, we consider the possibility of using the kinematics of the tagging jets in Higgs production via the vector boson fusion (VBF) process to test the tensor structure of the Higgs-vector boson ($HVV$) interaction and to determine the spin and CP properties of the observed resonance. We show that an anomalous $HVV$ vertex, in particular its explicit momentum dependence, drastically affects the rapidity between the two scattered quarks and their transverse momenta and, hence, the acceptance of the kinematical cuts that allow to select the VBF topology. Read More

We survey the expected polarization of the top produced in the decay of a scalar top quark, $\tilde t \rightarrow {\tilde t}\chi_i^0, i =1-2$. The phenomenology is quite interesting, since the expected polarization depends both on the mixing in the stop and neutralino sectors and on the mass differences between the stop and the neutralino. We find that a mixed stop behaves almost like a right-handed stop due to the larger hypercharge that enters the stop/top/gaugino coupling and that these polarisation effects disappear, when $m_{\tilde t_1} \approx m_t+m_{\tilde\chi^0_i}$. Read More

While the recent discovery of a Higgs-like boson at the LHC is an extremely important and encouraging step towards the discovery of the {\it complete} standard model(SM), the current information on this state does not rule out possibility of beyond standard model (BSM) physics. In fact the current data can still accommodate reasonable values of the branching fractions of the Higgs into a channel with `invisible' decay products, such a channel being also well motivated theoretically. In this study we revisit the possibility of detecting the Higgs in this invisible channel for both choices of the LHC energies, 8 and 14 TeV, for two production channels; vector boson fusion(VBF) and associated production($ZH$). Read More

2012Nov
Authors: J. L. Abelleira Fernandez, C. Adolphsen, P. Adzic, A. N. Akay, H. Aksakal, J. L. Albacete, B. Allanach, S. Alekhin, P. Allport, V. Andreev, R. B. Appleby, E. Arikan, N. Armesto, G. Azuelos, M. Bai, D. Barber, J. Bartels, O. Behnke, J. Behr, A. S. Belyaev, I. Ben-Zvi, N. Bernard, S. Bertolucci, S. Bettoni, S. Biswal, J. Blümlein, H. Böttcher, A. Bogacz, C. Bracco, J. Bracinik, G. Brandt, H. Braun, S. Brodsky, O. Brüning, E. Bulyak, A. Buniatyan, H. Burkhardt, I. T. Cakir, O. Cakir, R. Calaga, A. Caldwell, V. Cetinkaya, V. Chekelian, E. Ciapala, R. Ciftci, A. K. Ciftci, B. A. Cole, J. C. Collins, O. Dadoun, J. Dainton, A. De. Roeck, D. d'Enterria, P. DiNezza, M. D'Onofrio, A. Dudarev, A. Eide, R. Enberg, E. Eroglu, K. J. Eskola, L. Favart, M. Fitterer, S. Forte, A. Gaddi, P. Gambino, H. García Morales, T. Gehrmann, P. Gladkikh, C. Glasman, A. Glazov, R. Godbole, B. Goddard, T. Greenshaw, A. Guffanti, V. Guzey, C. Gwenlan, T. Han, Y. Hao, F. Haug, W. Herr, A. Hervé, B. J. Holzer, M. Ishitsuka, M. Jacquet, B. Jeanneret, E. Jensen, J. M. Jimenez, J. M. Jowett, H. Jung, H. Karadeniz, D. Kayran, A. Kilic, K. Kimura, R. Klees, M. Klein, U. Klein, T. Kluge, F. Kocak, M. Korostelev, A. Kosmicki, P. Kostka, H. Kowalski, M. Kraemer, G. Kramer, D. Kuchler, M. Kuze, T. Lappi, P. Laycock, E. Levichev, S. Levonian, V. N. Litvinenko, A. Lombardi, J. Maeda, C. Marquet, B. Mellado, K. H. Mess, A. Milanese, J. G. Milhano, S. Moch, I. I. Morozov, Y. Muttoni, S. Myers, S. Nandi, Z. Nergiz, P. R. Newman, T. Omori, J. Osborne, E. Paoloni, Y. Papaphilippou, C. Pascaud, H. Paukkunen, E. Perez, T. Pieloni, E. Pilicer, B. Pire, R. Placakyte, A. Polini, V. Ptitsyn, Y. Pupkov, V. Radescu, S. Raychaudhuri, L. Rinolfi, E. Rizvi, R. Rohini, J. Rojo, S. Russenschuck, M. Sahin, C. A. Salgado, K. Sampei, R. Sassot, E. Sauvan, M. Schaefer, U. Schneekloth, T. Schörner-Sadenius, D. Schulte, A. Senol, A. Seryi, P. Sievers, A. N. Skrinsky, W. Smith, D. South, H. Spiesberger, A. M. Stasto, M. Strikman, M. Sullivan, S. Sultansoy, Y. P. Sun, B. Surrow, L. Szymanowski, P. Taels, I. Tapan, T. Tasci, E. Tassi, H. Ten. Kate, J. Terron, H. Thiesen, L. Thompson, P. Thompson, K. Tokushuku, R. Tomás García, D. Tommasini, D. Trbojevic, N. Tsoupas, J. Tuckmantel, S. Turkoz, T. N. Trinh, K. Tywoniuk, G. Unel, T. Ullrich, J. Urakawa, P. VanMechelen, A. Variola, R. Veness, A. Vivoli, P. Vobly, J. Wagner, R. Wallny, S. Wallon, G. Watt, C. Weiss, U. A. Wiedemann, U. Wienands, F. Willeke, B. -W. Xiao, V. Yakimenko, A. F. Zarnecki, Z. Zhang, F. Zimmermann, R. Zlebcik, F. Zomer

The present note relies on the recently published conceptual design report of the LHeC and extends the first contribution to the European strategy debate in emphasising the role of the LHeC to complement and complete the high luminosity LHC programme. The brief discussion therefore focuses on the importance of high precision PDF and $\alpha_s$ determinations for the physics beyond the Standard Model (GUTs, SUSY, Higgs). Emphasis is also given to the importance of high parton density phenomena in nuclei and their relevance to the heavy ion physics programme at the LHC. Read More

2012Nov
Authors: J. L. Abelleira Fernandez, C. Adolphsen, P. Adzic, A. N. Akay, H. Aksakal, J. L. Albacete, B. Allanach, S. Alekhin, P. Allport, V. Andreev, R. B. Appleby, E. Arikan, N. Armesto, G. Azuelos, M. Bai, D. Barber, J. Bartels, O. Behnke, J. Behr, A. S. Belyaev, I. Ben-Zvi, N. Bernard, S. Bertolucci, S. Bettoni, S. Biswal, J. Blümlein, H. Böttcher, A. Bogacz, C. Bracco, J. Bracinik, G. Brandt, H. Braun, S. Brodsky, O. Brüning, E. Bulyak, A. Buniatyan, H. Burkhardt, I. T. Cakir, O. Cakir, R. Calaga, A. Caldwell, V. Cetinkaya, V. Chekelian, E. Ciapala, R. Ciftci, A. K. Ciftci, B. A. Cole, J. C. Collins, O. Dadoun, J. Dainton, A. De. Roeck, D. d'Enterria, P. DiNezza, M. D'Onofrio, A. Dudarev, A. Eide, R. Enberg, E. Eroglu, K. J. Eskola, L. Favart, M. Fitterer, S. Forte, A. Gaddi, P. Gambino, H. García Morales, T. Gehrmann, P. Gladkikh, C. Glasman, A. Glazov, R. Godbole, B. Goddard, T. Greenshaw, A. Guffanti, V. Guzey, C. Gwenlan, T. Han, Y. Hao, F. Haug, W. Herr, A. Hervé, B. J. Holzer, M. Ishitsuka, M. Jacquet, B. Jeanneret, E. Jensen, J. M. Jimenez, J. M. Jowett, H. Jung, H. Karadeniz, D. Kayran, A. Kilic, K. Kimura, R. Klees, M. Klein, U. Klein, T. Kluge, F. Kocak, M. Korostelev, A. Kosmicki, P. Kostka, H. Kowalski, M. Kraemer, G. Kramer, D. Kuchler, M. Kuze, T. Lappi, P. Laycock, E. Levichev, S. Levonian, V. N. Litvinenko, A. Lombardi, J. Maeda, C. Marquet, B. Mellado, K. H. Mess, A. Milanese, J. G. Milhano, S. Moch, I. I. Morozov, Y. Muttoni, S. Myers, S. Nandi, Z. Nergiz, P. R. Newman, T. Omori, J. Osborne, E. Paoloni, Y. Papaphilippou, C. Pascaud, H. Paukkunen, E. Perez, T. Pieloni, E. Pilicer, B. Pire, R. Placakyte, A. Polini, V. Ptitsyn, Y. Pupkov, V. Radescu, S. Raychaudhuri, L. Rinolfi, E. Rizvi, R. Rohini, J. Rojo, S. Russenschuck, M. Sahin, C. A. Salgado, K. Sampei, R. Sassot, E. Sauvan, M. Schaefer, U. Schneekloth, T. Schörner-Sadenius, D. Schulte, A. Senol, A. Seryi, P. Sievers, A. N. Skrinsky, W. Smith, D. South, H. Spiesberger, A. M. Stasto, M. Strikman, M. Sullivan, S. Sultansoy, Y. P. Sun, B. Surrow, L. Szymanowski, P. Taels, I. Tapan, T. Tasci, E. Tassi, H. Ten. Kate, J. Terron, H. Thiesen, L. Thompson, P. Thompson, K. Tokushuku, R. Tomás García, D. Tommasini, D. Trbojevic, N. Tsoupas, J. Tuckmantel, S. Turkoz, T. N. Trinh, K. Tywoniuk, G. Unel, T. Ullrich, J. Urakawa, P. VanMechelen, A. Variola, R. Veness, A. Vivoli, P. Vobly, J. Wagner, R. Wallny, S. Wallon, G. Watt, C. Weiss, U. A. Wiedemann, U. Wienands, F. Willeke, B. -W. Xiao, V. Yakimenko, A. F. Zarnecki, Z. Zhang, F. Zimmermann, R. Zlebcik, F. Zomer

This document provides a brief overview of the recently published report on the design of the Large Hadron Electron Collider (LHeC), which comprises its physics programme, accelerator physics, technology and main detector concepts. The LHeC exploits and develops challenging, though principally existing, accelerator and detector technologies. This summary is complemented by brief illustrations of some of the highlights of the physics programme, which relies on a vastly extended kinematic range, luminosity and unprecedented precision in deep inelastic scattering. Read More

We revisit the issue of considering stochasticity of Grassmannian coordinates in N=1 superspace, which was analyzed previously by Kobakhidze {\it et al}. In this stochastic supersymmetry(SUSY) framework, the soft SUSY breaking terms of the minimal supersymmetric Standard Model(MSSM) such as the bilinear Higgs mixing, trilinear coupling as well as the gaugino mass parameters are all proportional to a single mass parameter \xi, a measure of supersymmetry breaking arising out of stochasticity. While a nonvanishing trilinear coupling at the high scale is a natural outcome of the framework, a favorable signature for obtaining the lighter Higgs boson mass $m_h$ at 125 GeV, the model produces tachyonic sleptons or staus turning to be too light. Read More

We propose measurement of transverse single spin asymmetry (SSA) in charmonium production as a probe of gluon Sivers function. We estimate SSA in low virtuality electroproduction of $J/\psi $ using color evaporation model of charmonium production and existing models of the gluon Sivers function and find sizable asymmetry at JLab, HERMES, COMPASS and eRHIC energies. Read More

This document presents an overview of the physics potential of a future electron-positron linear collider. It represents a common input from the CLIC and ILC communities. Read More

The Higgs boson with a mass $M_H \approx 126$ GeV has been observed by the ATLAS and CMS experiments at the LHC and a total significance of about five standard deviations has been reported by both collaborations when the channels $H\to \gamma \gamma$ and $H\to ZZ \to 4\ell$ are combined. Nevertheless, while the rates in the later search channel appear to be in accord with those predicted in the Standard Model, there seems to be an excess of data in the case of the $H\to \gamma\gamma$ discovery channel. Before invoking new physics contributions to explain this excess in the di--photon Higgs rate, one should verify that standard QCD effects cannot account for it. Read More

We report on a recent investigation of the single spin asymmetry (SSA) in low virtuality electroproduction of $J/\psi$ in color evaporation model. We show that this can be used as a probe for the still unknown gluon Sivers function. Read More

2012Jun
Authors: J. L. Abelleira Fernandez, C. Adolphsen, A. N. Akay, H. Aksakal, J. L. Albacete, S. Alekhin, P. Allport, V. Andreev, R. B. Appleby, E. Arikan, N. Armesto, G. Azuelos, M. Bai, D. Barber, J. Bartels, O. Behnke, J. Behr, A. S. Belyaev, I. Ben-Zvi, N. Bernard, S. Bertolucci, S. Bettoni, S. Biswal, J. Blümlein, H. Böttcher, A. Bogacz, C. Bracco, G. Brandt, H. Braun, S. Brodsky, O. Brüning, E. Bulyak, A. Buniatyan, H. Burkhardt, I. T. Cakir, O. Cakir, R. Calaga, V. Cetinkaya, E. Ciapala, R. Ciftci, A. K. Ciftci, B. A. Cole, J. C. Collins, O. Dadoun, J. Dainton, A. De. Roeck, D. d'Enterria, A. Dudarev, A. Eide, R. Enberg, E. Eroglu, K. J. Eskola, L. Favart, M. Fitterer, S. Forte, A. Gaddi, P. Gambino, H. García Morales, T. Gehrmann, P. Gladkikh, C. Glasman, R. Godbole, B. Goddard, T. Greenshaw, A. Guffanti, V. Guzey, C. Gwenlan, T. Han, Y. Hao, F. Haug, W. Herr, A. Hervé, B. J. Holzer, M. Ishitsuka, M. Jacquet, B. Jeanneret, J. M. Jimenez, J. M. Jowett, H. Jung, H. Karadeniz, D. Kayran, A. Kilic, K. Kimura, M. Klein, U. Klein, T. Kluge, F. Kocak, M. Korostelev, A. Kosmicki, P. Kostka, H. Kowalski, G. Kramer, D. Kuchler, M. Kuze, T. Lappi, P. Laycock, E. Levichev, S. Levonian, V. N. Litvinenko, A. Lombardi, J. Maeda, C. Marquet, S. J. Maxfield, B. Mellado, K. H. Mess, A. Milanese, S. Moch, I. I. Morozov, Y. Muttoni, S. Myers, S. Nandi, Z. Nergiz, P. R. Newman, T. Omori, J. Osborne, E. Paoloni, Y. Papaphilippou, C. Pascaud, H. Paukkunen, E. Perez, T. Pieloni, E. Pilicer, B. Pire, R. Placakyte, A. Polini, V. Ptitsyn, Y. Pupkov, V. Radescu, S. Raychaudhuri, L. Rinolfi, R. Rohini, J. Rojo, S. Russenschuck, M. Sahin, C. A. Salgado, K. Sampei, R. Sassot, E. Sauvan, U. Schneekloth, T. Schörner-Sadenius, D. Schulte, A. Senol, A. Seryi, P. Sievers, A. N. Skrinsky, W. Smith, H. Spiesberger, A. M. Stasto, M. Strikman, M. Sullivan, S. Sultansoy, Y. P. Sun, B. Surrow, L. Szymanowski, P. Taels, I. Tapan, A. T. Tasci, E. Tassi, H. Ten. Kate, J. Terron, H. Thiesen, L. Thompson, K. Tokushuku, R. Tomás García, D. Tommasini, D. Trbojevic, N. Tsoupas, J. Tuckmantel, S. Turkoz, T. N. Trinh, K. Tywoniuk, G. Unel, J. Urakawa, P. VanMechelen, A. Variola, R. Veness, A. Vivoli, P. Vobly, J. Wagner, R. Wallny, S. Wallon, G. Watt, C. Weiss, U. A. Wiedemann, U. Wienands, F. Willeke, B. -W. Xiao, V. Yakimenko, A. F. Zarnecki, Z. Zhang, F. Zimmermann, R. Zlebcik, F. Zomer

The physics programme and the design are described of a new collider for particle and nuclear physics, the Large Hadron Electron Collider (LHeC), in which a newly built electron beam of 60 GeV, up to possibly 140 GeV, energy collides with the intense hadron beams of the LHC. Compared to HERA, the kinematic range covered is extended by a factor of twenty in the negative four-momentum squared, $Q^2$, and in the inverse Bjorken $x$, while with the design luminosity of $10^{33}$ cm$^{-2}$s$^{-1}$ the LHeC is projected to exceed the integrated HERA luminosity by two orders of magnitude. The physics programme is devoted to an exploration of the energy frontier, complementing the LHC and its discovery potential for physics beyond the Standard Model with high precision deep inelastic scattering measurements. Read More

In the context of the Standard model with a fourth generation, we explore the allowed mass spectra in the fourth generation quark and lepton sectors as functions of the Higgs mass. Using the constraints from unitarity and oblique parameters, we show that a heavy Higgs allows large mass splittings in these sectors, opening up new decay channels involving W emission. A Higgs heavier than $ \sim 800 GeV $ would in fact necessitate either a heavy quark decay channel t'-> b'W/b'-> t' W or a heavy lepton decay channel \tau' -> \nu' W as long as the mixing between the third and fourth generations is small. Read More

A high energy ep collider, such as the proposed LHeC, possesses the unique facility of permitting direct measurement of the HWW coupling without contamination from the HZZ coupling. At such a machine, the fusion of two W bosons through the HWW vertex would give rise to typical charged current (CC) events accompanied by a Higgs boson. We demonstrate that azimuthal angle correlations between the observable CC final states could then be a sensitive probe of the nature of the HWW vertex and hence of the CP properties of the Higgs boson. Read More

2012Mar
Authors: G. Brooijmans, B. Gripaios, F. Moortgat, J. Santiago, P. Skands, D. Albornoz Vásquez, B. C. Allanach, A. Alloul, A. Arbey, A. Azatov, H. Baer, C. Balázs, A. Barr, L. Basso, M. Battaglia, P. Bechtle, G. Bélanger, A. Belyaev, K. Benslama, L. Bergström, A. Bharucha, C. Boehm, M. Bondarenko, O. Bondu, E. Boos, F. Boudjema, T. Bringmann, M. Brown, V. Bunichev, S. Calvet, M. Campanelli, A. Carmona, D. G. Cerdeño, M. Chala, R. S. Chivukula, D. Chowdhury, N. D. Christensen, M. Cirelli, S. Cox, K. Cranmer, J. Da Silva, T. Delahaye, A. De Roeck, A. Djouadi, E. Dobson, M. Dolan, F. Donato, G. Drieu La Rochelle, G. Duda, C. Duhr, B. Dumont, J. Edsjö, J. Ellis, C. Evoli, A. Falkowski, M. Felcini, B. Fuks, E. Gabrielli, D. Gaggero, S. Gascon-Shotkin, D. K. Ghosh, A. Giammanco, R. M. Godbole, P. Gondolo, T. Goto, D. Grasso, P. Gris, D. Guadagnoli, J. F. Gunion, U. Haisch, L. Hartgring, S. Heinemeyer, M. Hirsch, J. Hewett, A. Ismail, T. Jeltema, M. Kadastik, M. Kakizaki, K. Kannike, S. Khalil, J-L. Kneur, M. Krämer, S. Kraml, S. Kreiss, J. Lavalle, R. Leane, J. Lykken, L. Maccione, F. Mahmoudi, M. Mangano, S. P. Martin, D. Maurin, G. Moreau, S. Moretti, I. Moskalenko, G. Moultaka, M. Muhlleitner, I. Niessen, B. O'Leary, E. Orlando, P. Panci, G. Polesello, W. Porod, T. Porter, S. Profumo, H. Prosper, A. Pukhov, A. Racioppi, M. Raidal, M. Rausch de Traubenberg, A. Renaud, J. Reuter, T. G. Rizzo, T. Robens, A. Y. Rodríguez-Marrero, P. Salati, C. Savage, P. Scott, S. Sekmen, A. Semenov, C. -L. Shan, C. Shepherd-Themistocleous, E. H. Simmons, P. Slavich, C. Speckner, F. Staub, A. Strong, R. Taillet, F. S. Thomas, M. C. Thomas, I. Tomalin, M. Tytgat, M. Ughetto, L. Valéry, D. G. E. Walker, A. Weiler, S. M. West, C. D. White, A. J. Williams, A. Wingerter, C. Wymant, J. -H. Yu, C. -P. Yuan, D. Zerwas

We present the activities of the "New Physics" working group for the "Physics at TeV Colliders" workshop (Les Houches, France, 30 May-17 June, 2011). Our report includes new agreements on formats for interfaces between computational tools, new tool developments, important signatures for searches at the LHC, recommendations for presentation of LHC search results, as well as additional phenomenological studies. Read More

We discuss the possibility of using electroproduction of $J/\psi $ as a probe of gluon Sivers function by measuring single spin asymmetry (SSA) in experiments with transversely polarized protons and electron beams. We estimate SSA for JLab, HERMES, COMPASS and eRHIC energies using the color evaporation model of charmonium production and find asymmetry up to 25% for certain choices of model parameters which have been used earlier for estimating SSA in the SIDIS and Drell-Yan processes. Read More

We investigate the expectations for the light Higgs signal in the MSSM in different search channels at the LHC. After taking into account dark matter and flavor constraints in the MSSM with eleven free parameters, we show that the light Higgs signal in the $gamma\gamma$ channel is expected to be at most at the level of the SM Higgs, while the $h\rightarrow b\bar{b}$ from W fusion and/or the $h \rightarrow\tau\bar\tau$ can be enhanced. For the main discovery mode, we show that a strong suppression of the signal occurs in two different cases: low $M_A$ or large invisible width. Read More

The search for heavy resonances in the dijet channel is part of the on-going physics programme, both at the Tevatron and at the LHC. Lower limits have been placed on the masses of dijet resonances predicted in a wide variety of models. However, across experiments, the search strategy assumes that the effect of the new particles is well-approximated by on-shell production and subsequent decay into a pair of jets. Read More

The polarisation of top quarks produced in high energy processes can be a very sensitive probe of physics beyond the Standard Model. The kinematical distributions of the decay products of the top quark can provide clean information on the polarisation of the produced top and thus can probe new physics effects in the top quark sector. We study some of the recently proposed polarisation observables involving the decay products of the top quark in the context of $H^-t$ and $Wt$ production. Read More