abstract

The comparison of samples with different number of charged leptons shows that trilepton signals are the most significant ones for seesaw mediators. As previously pointed out, this is indeed the case for scalar \({\mit \Delta }\) (type II) and fermion \({\mit \Sigma }\) (type III) triplets at LHC, which can be discovered in this channel for masses up to 500–700 GeV and an integrated luminosity of 30 fb\(^{-1}\); whereas fermion singlets \(N\) (type I) are marginally observable if there are no further new physics near the TeV scale. However, if there are new gauge interactions at this scale coupling to right-handed neutrinos, as in left–right models, heavy neutrinos are observable up to masses \(\sim 2\) TeV for new gauge boson masses up to \(\sim 4\) TeV, as we discuss in some detail.

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The hybrid \(N=1\)/\(N=2\) supersymmetric model predicts scalar gluons (sgluons) as SUSY partners of the Dirac gluino. Their strikingly distinct phenomenology at the CERN Large Hadron Collider is discussed.

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We review the electromagnetic form factor of heavy quarks with emphasis on the QCD radiative corrections at two-loop order in the perturbative expansion. We discuss important properties of the heavy-quark form factor such as its exponentiation in the high-energy limit and its role in QCD factorization theorems for massive \(n\)-parton amplitudes.

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We discuss jet production at forward rapidities at the LHC. In this region QCD logarithmic corrections in the hard transverse momentum and in the large rapidity interval may both be quantitatively significant. We describe results of using high-energy factorization techniques, which allow one to take into account both kinds of corrections to higher orders in QCD.

abstract

In this contribution, we summarize the results from an NLO computation of the production of \(t\bar {t}b\bar {b}\) in hadronic collisions. The results are obtained by combining two programs: Helac-1Loop, based on the OPP method and the reduction code CutTools, for the virtual one-loop matrix elements and Helac-Dipoles for the real-emission contributions. Selected numerical results are presented for the LHC.

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We derive the first four terms of an expansion in \(m_H^2\) / \(M_{t}^2\) of the total Higgs cross-section through gluon fusion. At NLO we demonstrate the excellent convergence of this series to the known result keeping the exact top mass dependence. At NNLO there is no known exact result, and our work represents a thorough quantitative investigation of the effects of finite top mass at this order. We discuss the applicability of our approach, and present numerical results for the LHC and Tevatron.

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We review recent developments and results for performing high precision calculations in the Minimal Supersymmetric Extension of the Standard Model (MSSM). As an example, the effects of the three-loop order radiative corrections on the unification of the gauge couplings will be discussed in some details.

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After a general introduction about the latest developments in the approach to multi-loop NLO calculations, we present a numerical evaluation of the one-loop QED corrections to the hard-bremsstrahlung emission in Bhabha scattering. The calculation is performed by employing the reduction method developed by Ossola, Papadopoulos and Pittau (OPP).

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We use the phenomenological valon model to extract polarized parton densities and polarized proton structure function. Since the analytical result at large values of \(x\) and low values of \(Q^{2}\) is not in good agreement with available experimental data, we employ target mass correction to increase the reliability of the calculations. New comparison confirms a better agreement with the experimental data.

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We perform N\(^3\)LO QCD analysis of the world data on the unpolarized DIS structure functions to determine \(\alpha _{\rm s}\) and valance quark distributions with fully correlated errors. Due to increasing the accuracy of DIS experiments and reduction the experimental errors on determining the strong coupling constant, the higher order analysis is required. The Padé approximations are used to estimate the 4-loop anomalous dimension. We consider the non-singlet sector of parton distributions in our calculations. A comparison of the N\(^3\)LO/N\(^2\)LO with N\(^3\)LO/NLO ratios for up and down valence quark distributions indicate outstanding influence of the higher order analysis.

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The status of the future linear collider projects, ILC and CLIC, is presented.

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Our current knowledge of \({\cal B}(\bar B \to X_s \gamma )\) is briefly summarized, with particular attention to uncertain non-perturbative effects.

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The HBT method is used to get information about the sizes, shapes and sometimes also about the time evolution of the homogeneity regions in hadroproduction processes. Homogeneity region \(\mathbf {K}\) is the region, where the hadrons with momentum \(\mathbf {K}\) are produced. The shape and size of homogeneity region \(\mathbf {K}\) is described by the Wigner function \(W(\mathbf {K},\mathbf {X})\) evaluated in the interaction representation after all the hadrons had been produced. Additional information about the evolution in time is contained in the emission function \(S(K,X)\). A theorem is presented and discussed which specifies which of the parameters characterizing the Wigner function can and which cannot be measured using the HBT method. In order to obtain the complete Wigner function additional assumptions are needed. For instance, it is enough to know the distribution of the centers of the homogeneity regions \(\langle \mathbf {X} \rangle _{\mathbf {K}}\). In order to find the emission function further assumptions are required. No systematic analysis is available, but some instructive examples are discussed.

abstract

We argue that adding gauge-singlet real scalars to the Standard Model can both ameliorate the little hierarchy problem and provide a realistic source of Dark Matter. Masses of the scalars should be in the 1–3 TeV range, while the lowest cutoff of the (unspecified) UV completion of the model must be \( \gtrsim 5\) TeV, depending on the Higgs boson mass and the number of singlets present. The scalars couple to the Majorana mass term for right-handed neutrinos implying one massless neutrino. The resulting mixing angles are consistent with the tri-bimaximal mixing scenario.

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We discuss the reaction of associated production of a top quark pair and a Higgs boson at the future \(e^+e^-\) linear collider that can be used to determine the top-Higgs Yukawa coupling. Taking into account decays of the top quarks and the light Higgs boson leads to reactions with 8 fermions in the final state which, in the framework of the Standard Model, receive contributions typically from many thousands Feynman diagrams. An overwhelming majority of the diagrams comprises the off resonance background to the resonant signal of associated production and decay of the top quark pair and Higgs boson. We address the signal and background issue by comparing cross-sections calculated with the signal diagrams only and with the complete sets of the diagrams.

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Keeping in mind the possibility of large \(\theta _{13}\), which will be soon explored by reactor and accelerator experiments, I formulate a perturbation theory of neutrino oscillation under the ansatz \(s_{13}^2 \simeq \Delta m^2_{21}\) / \( \Delta m^2_{31}\equiv \varepsilon \simeq 0.03\), which is comparable to the Chooz limit. Under the framework, I derive the perturbative formula of the \(\nu _{e}\) appearance probability valid to the order of \(\varepsilon ^2\) in which effects of arbitrary matter density profile is taken into account. I use the formula to analyze problem of possible obstruction to detecting lepton CP violation by effects of asymmetry in matter density profile. Though the asymmetry could be large for neutrino trajectories which traverse both continental and sea crust, its effect on obscuring CP violation measurement is found to be quite small.

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Basic aspects of phononless resonant capture of monoenergetic electron antineutrinos (Mössbauer antineutrinos) emitted in bound-state \(\beta \)-decay in the \(^{3}\)H–\(^{3}\)He system are considered. It is shown that stochastic magnetic relaxation phenomena as well as the direct influence of solid-state effects on the energy of the \(\bar {\nu _{e}}\) will cause line broadening by a factor of more than \(10^{13}\). Lattice expansion and contraction after the transformation of the nucleus will drastically reduce the probability for phononless transitions. Thus, the observation of Mössbauer \(\bar {\nu _{e}}\) of the \(^{3}\)H–\(^{3}\)He system will most probably be unsuccessful. As a possible alternative, the rare-earth system \(^{163}\)Ho–\(^{163}\)Dy is briefly discussed.

abstract

Neutrinos produced in the muon decay scatter on electrons in the near (without oscillation) and in the far detector (after oscillation) and the number of produced muons is observed. In the frame of the Standard Model the cross-section for muon production does not depend on the neutrino nature. The situation is different, if beyond the SM neutrino interactions are present. We use the Fermi contact model, where we allow only one additional coupling, the charged scalar right-handed coupling which appear in variety of models. No bounds on the new scalar coupling for Majorana neutrino are found. The cross-sections for muon production is different for Dirac and Majorana neutrinos giving in principle possibility to distinguish their nature. The differences between the Dirac and Majorana cross-sections appear in the near and in the far detector. The cross-section for both types of neutrinos is different even if neutrinos do not oscillate, but the difference is larger after oscillation, even in the vacuum.

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With a mass of about 600 tons of Liquid Argon (LAr), the ICARUS T600 detector is the biggest, up to now, LAr Time Projection Chamber (TPC). Following its successful test run, on the Earth surface, in Pavia (Italy) in 2001, the detector is now very close to start data taking in the Gran Sasso underground laboratory. The main features of the LAr TPC technique, together with a short discussion of some of the ICARUS T600 test run results, are presented in this paper.

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I give a brief summary on the status of Dark Matter (DM) explanations of the annual modulation signal observed in DAMA/LIBRA. I stress that for spin-independent elastic scattering the issue of ion channeling is crucial. While in the presence of channeling a marginal compatibility is obtained between DAMA and other constraints, the DM interpretation is strongly disfavoured without channeling. A similar situation — though slightly less conclusive — applies also in the cases of spin-dependent and inelastic DM scattering.

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In this report, some research results of the neutrino astrophysics group at the Institute of Physics of Jagellonian University are presented http://ribes.if.uj.edu.pl/psns. It is shown that neutrinos emitted by presupernovae located within a few kpc from Earth could be detected by new generation of neutrino detectors. We encourage planners of the future neutrino experiments to include presupernova neutrino measurements on their agenda.

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The extended nonlinear model has been applied to construct neutron star matter equation of state. In the case of neutron star matter with non-zero strangeness the extension of the vector meson sector by the inclusion of nonlinear mixed terms results in the stiffening of the equation of state and accordingly in the higher value of the maximum neutron star mass.

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The relation of some small exotic smooth \(\mathbb {R}^{\,4}\) with Abelian gerbes and \(H\)-deformed generalized Hitchin’s structures on \(S^{\,3}\subset \mathbb {R}^{\,4}\) is discussed. Exotic smoothness of \(\mathbb {R}^{\,4}\) appears as some fundamental phenomenon related to string theory and which has not been taken into account yet in construction of any QG theory.

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Recent results on \(\tau \) lepton physics predominantly coming from the BaBar and Belle detectors are discussed.

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I review recent progress in the prediction of the muon \(g-2\). The main issue are those contributions which cannot be calculated by perturbative means: the hadronic higher order effects which come into play at \(O(\alpha ^2)\) and the hadronic light–by–light scattering contribution at the order of \(O(\alpha ^3)\).

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We present a new scheme of a fully exclusive QCD NLO parton shower for the initial state. The scheme is based on the collinear factorization, but at the same time it provides fully exclusive events with four-momenta of all emitted partons. We show a first working prototype of such a MC code for the subset of graphs for the Non Singlet evolution and we show that on the inclusive level it reproduces the standard \(\overline {\rm MS}\) DGLAP results.

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An efficient numerical algorithm to evaluate one-loop amplitudes is presented. It expresses the amplitude in terms of universal tensor integrals and their process-dependent coefficients, both of which are calculated with recursive methods. It is shown by explicit calculations that for ordered QCD amplitudes with a number of external legs up to 10, its performance is competitive with other methods.

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We report on a numerical implementation of the QED one-loop 5-point functions. These functions contribute to the NLO corrections to the hard-bremsstrahlung process \(e^+ e^- \to \mu ^+ \mu ^- \gamma \), which is an important background process for accurate predictions in experiments at high luminosity meson factories such as DAFNE and PEP-II. The calculation is implemented using publicly available tools and incorporates several numerical and analytical cross-checks. Numerical precision and stability is demonstrated by preliminary test runs with KLOE and BarBar kinematical cuts.

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We calculate the two- and three-loop massive operator matrix element (OME) contributing to the heavy flavor Wilson coefficients of transversity. We obtain the complete result for the two-loop OME and compute the first thirteen Mellin moments at three-loop order. As a by-product of the calculation, the moments \(N=1\) to \(13\) of the complete two-loop and the \(T_F\)-part of the three-loop transversity anomalous dimension are obtained.

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We report on our study of the LFV processes \({\mu \to e\gamma }\), \({\mu \to e e \overline {e}}\) and \({\mu N \to e N}\) in the context of Little Higgs models. Specifically, we examine the Littlest Higgs with T-parity (LHT) and the Simplest Little Higgs (SLH) as examples of a Product group and Simple group Little Higgs models, respectively. The necessary Feynman rules for both models are obtained in the ’t Hooft Feynman Gauge up to the order of \(v^2\) / \(f^{\,2}\) and predictions for the branching ratios and conversion rates of the LFV processes are calculated to leading order (one-loop level). Comparison with current experimental constraints show that there is some tension and, in order to be within the limits, one requires a higher breaking scale \(f\), alignment of the heavy and light lepton sectors or almost degenerate heavy lepton masses. These constraints are more demanding in the SLH than in the LHT case.

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We discuss some cosmological features of a hypothetical type of new physics characterized by begin asymptotically free in the UV regime and conformally invariant in the IR. We show that nucleosynthesis data generates non-trivial constrains this type of models.

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The problem of possible astrophysical consequences of the existence of exotic differential structures on manifolds is discussed. It is argued that corrections to the curvature of the form of a source like terms should be expected in the Einstein equations if they are written in the “wrong” differential structure. Examples of topologically trivial spaces on which exotic differential structures act as a source of gravitational force even in the absence of matter are given. Propagation of light in the presence of such phenomena is also discussed. A brief review of exotic smoothness is added for completeness.

abstract

Matter budget in the Universe together with primordial nucleosynthesis bounds on baryonic density suggests that dark matter in galaxies should have non-baryonic nature. On the other hand, considerable agreement of a variety of astrophysical observations with standard physics can serve as a source of constraints on non-standard ideas. In this context we consider G117-B15A pulsating white dwarf for which the rate of period change of its fundamental mode has been accurately measured. This star has been claimed the most stable oscillator ever recorded in the optical band. Here we use this object to derive a bound on theories with large extra dimensions as well as to constrain supersymmetric dark matter.

abstract

The limits placed by the non-measurement of atomic and neutron electric dipole moments on CP violating phases beyond the SM are found to be not fully justified since the calculations of the expected EDMs lack the full understanding of the connection between perturbative and nonperturbative regimes of QCD for the measured bound states. As a consequence, rather old subroutines for the evaluation of EDMs are still usable.

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The neutrino oscillation data find a good approximation in the so-called tri-bimaximal pattern. Recently a paper appeared showing that also the bimaximal pattern, which is already ruled out by the measurements, could be a very good starting point in order to describe the lepton mixing. In this paper I review both the flavour structures and then I present an explicit flavour model based on the discrete group \({\rm S}_4\), in which the PMNS mixing matrix is of the bimaximal form in first approximation and after it receives corrections which bring it in agreement with the data. The resulting spectrum of light neutrinos shows a moderate normal hierarchy and is compatible, within large ambiguities, with the constraints from leptogenesis as an explanation of the baryon asymmetry in the Universe.

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To improve the accuracy of the \(e^+e^- \to \pi ^+\pi ^-\gamma \) Radiative Return Method, one has to control the theoretical uncertainty of the final-state photon emission. It is of particular importance at DAPHNE for the analysis, where cuts are relaxed to cover the threshold region. By means of Monte Carlo generator PHOKHARA we compare several final-state radiation models and present results, relevant for a meson factory running at \(\sqrt {s}=1\) GeV.