17554643
Center-edge asymmetry at hadron colliders
We investigate the possibility of using the center-edge asymmetry to distinguish graviton exchange from other new physics effects at hadron colliders. Specifically, we study lepton-pair production within the Arkani-Hamed\char21{}Dimopoulos\char21{}Dvali (ADD) and Randall-Sundrum (RS) scenarios. At the Fermilab Tevatron, the graviton-$Z$ interference is the most important contribution to the center-edge asymmetry, whereas at the CERN LHC, the dominant contribution comes from gluon fusion via graviton exchange, which has no analog at ${e}^{+}{e}^{\ensuremath{-}}$ colliders. We find that spin-2 and spin-1 exchange can be distinguished up to an ADD cutoff scale, ${M}_{H},$ of about 5 TeV, at the 95% C.L. In the RS scenario, spin-2 resonances can be identified in most of the favored parameter space.
121188774
IDENTIFICATION OF GRAVITON EXCHANGE EFFECTS AT HIGH ENERGY COLLIDERS
204940702
New Physics Effects in Fermion-Pair Production at e+e− Colliders
Fermion compositeness, and other types of new physics that can be described by the exchange of very massive particles, can manifest themselves as the result of an effective four-fermion contact interaction. In the case of the processes e+e− → μ+μ−, τ+τ−, b̄b and c̄c at future e+e− colliders with √s = 0.5 − 1 TeV, we examine the sensitivity to four-fermion contact interactions of two new integrated observables, σ+ and σ−, conveniently defined for such kind of analysis. We find that, if longitudinal polarization of the electron beam were available, these observables would offer the opportunity to separate the helicity cross sections and, in this way, to derive model-independent bounds on the relevant parameters.
119347724
Identification of Large Extra Spatial Dimensions at the LC
We discuss the possibility to cleanly distinguish, in electron-positron annihilation into fermion pairs at a high energy collider, the indirect manifestations of graviton exchange from those of four- fermion contact interactions. The method is based on cross section asymmetries emphasizing the spin-2 character of graviton exchange and is explicitly applied to the ADD scenario for gravity in extra dimensions. The availability of initial beams longitudinal polarization is also taken into account in the analysis. For typical c.m. energies and time-integrated luminosities foreseen at the International Linear Collider ( p s = 0.5 1 TeV, Lint = 50 1000 fb 1 ), a 5� identification reach of 3.5 5.8 TeV for the mass scale MH relevant to the ADD model can be obtained, while the size of the reach on the mass scalescharacterizing four-fermion contact interactions can be of the order of 45 65 TeV. I. INTRODUCTION In a variety of proposed new physics (NP) scenarios, non-standard interactions among the familiar Standard Model (SM) particles can be mediated by exchanges of new quantum states with mass scales expected to be much larger than the c.m. energy available at current (and perhaps future) colliders. Accordingly, only indirect manifestations of such high mass scales and their corresponding novel interactions can occur, through deviations of the measured cross sections from the SM predictions. The most convenient theoretical representation of such interactions is provided by the effective interaction framework, where the non-standard Hamiltonian is expanded in a series of specific local operators of increasing dimension, and accordingly the transition amplitudes for processes among the SM particles are power expanded in the (small) ratio between the 'low' c.m. machine energy and the relevant high mass scales. Generally, to limit the number of unknown parameters to be constrained (or determined) experimentally, the lowest-dimensional operator is retained in the expansion, assuming higher powers to be negligible due to the strong suppression by the large mass scale. Clearly, in this situation, NP searches are favoured by the signal enhancement due to the high energies and luminosities available at the planned linear colliders. A relevant aspect in this regard is that, in principle, different kinds of non-standard interactions may produce in the integrated cross sections similar deviations from the SM and, therefore, it is important to devise suitable observables that, given the expected experimental accuracy, can discriminate among the various, and competing, possible sources of a given deviation. Here, we will focus on the problem of cleanly identifying, in high energy e + e − → f ¯ f (f 6 e, t) at the International Linear Collider (ILC), signals of the ADD model of gravity in large, compactified, extra spatial dimensions with respect to the effects originating from four-fermion contact interactions. For this purpose, we shall use particular combinations of integrated cross sections, the so-called "center-edge asymmetries", sensitive to the
17588569
Model independent analysis of the trilinear gauge boson couplings at LC: role of polarized cross sections
By means of a model-independent analysis, we discuss the constraints on anomalous trilinear gauge-boson couplings that can be obtained from the study of electron-positron annihilation into $W$ pairs at LC with \sqrt{s}=0.5 TeV and 1 TeV. We consider the general CP conserving anomalous effective Lagrangian, as well as some specific models with reduced number of independent couplings. The analysis is based on combinations of observables with initial and final state polarizations, that allow to separately constrain the different couplings and to improve the corresponding numerical bounds.
18700563
Probing three boson anomalous coupling in e+ e- ----> W+ W- at future linear e+ e- colliders with polarized beams
We study the potential of the next-generation $e^+ e^-$ linear colliders with longitudinally polarized beams, to restrict the values of the anomalous trilinear couplings $WW\gamma$ and $WWZ$ from the measurement of the process $e^+ e^-\to W^+ W^-$. Along with initial $e^+e^-$ polarization, we account also for the possibilities offered by cross sections for polarized final $W$, in order to disentangle the constraints on the various constants. The results show the essential role of the initial beams polarization in improving the bounds obtained from the unpolarized case.
122314224
The Gigaton Volume Detector in Lake Baikal
Abstract The objective of the Baikal Project is the creation of a kilometer-scale high-energy neutrino observatory: the Gigaton Volume Detector (GVD) in Lake Baikal. Basic elements of the GVD – new optical modules, FADC readout units, and underwater communication systems – were investigated and tested in Lake Baikal with prototype strings in 2008–2010. We describe the results of prototype strings operation and review the preliminary design and expected sensitivity of the GVD telescope.