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A. A. Pankov

Publications and source records attributed to A. A. Pankov.

At least 37 records · Page 2Linked to original sources
arXiv2008

Spin identification of the Randall-Sundrum resonance in lepton-pair production at the LHC

The determination of the spin of the quantum states exchanged in the various non-standard interactions is a relevant aspect in the identification of the corresponding scenarios. We discuss the identification reach at LHC on the spin-2 of the lowest-lying Randall-Sundrum resonance, predicted by gravity with one warped extra dimension, against spin-1 and spin-0 non-standard exchanges with the same mass and producing the same number of events in the cross section. We focus on the angular distributions of leptons produced in the Drell-Yan process at the LHC, in particular we use as basic observable a normalized integrated angular asymmetry A_{CE}. Our finding is that the 95% C.L. identification reach on the spin-2 of the RS resonance (equivalently, the exclusion reach on both the spin-1 and spin-0 hypotheses for the peak) is up to a resonance mass scale of the order of 1.0 or 1.6 TeV in the case of weak coupling between graviton excitations and SM particles (k/{\bar M}_{Pl}=0.01) and 2.4 or 3.2 TeV for larger coupling constant (k/{\bar M}_{Pl}=0.1) for a time-integrated LHC luminosity of 10 or 100 fb^{-1}, respectively. Also, some comments are given on the complementary rôles of the angular analysis and the eventual discovery of the predicted second graviton excitation in the identification of the RS scenario.

hep-ph↗
arXiv2007

Discovery and Identification of Contactlike Interactions in Fermion-pair Production at ILC

Non-standard scenarios described by effective contactlike interactions can be revealed only by searching for deviations of the measured observables from the Standard Model (SM) predictions. If deviations were indeed observed within the experimental uncertainty, the identification of their source among the different non-standard interactions should be needed. We here consider the example of the discrimination of gravity in compactified extra dimensions (ADD model) against the four-fermion contact interactions (CI). We present assessments of the identification reach on this scenario, that could be obtained from measurements of the differential cross sections for the fermionic processes $e^+e^-\to{\bar f}f$, with $f=e,μ,τ,c,b$, at the planned ILC.

hep-ph↗
arXiv2006

Revealing the large extra dimension effective interaction at an e^+e^- collider with polarized beams

Contactlike nonstandard effective interactions can be revealed through deviations of observables from the Standard Model predictions. If such deviations were observed, the relevant source should be identified among the possible models that could explain them. We estimate the expected discrimination reach on the ADD model of gravity in large compactified extra dimensions, against the compositeness-inspired four-fermion contact interaction. As basic observables we take the differential cross sections for fermion-pair production at a 0.5-1 TeV electron-positron linear collider with both beams longitudinally polarized. For the four-fermion contact interaction, we assume a general linear combination of the individual models with definite chiralities, and arbitrary coupling constants. Accordingly, the estimated identification reach on the ADD scenario can be considered as `model-independent'. We emphasize the substantial role of beams polarization in enhancing the identification sensitivity.

hep-ph↗
arXiv2006

Distinguishing new physics scenarios with polarized electron and positron beams

Contactlike nonstandard interactions can be revealed only through deviations of observables from the standard model predictions. We consider a number of such nonstandard scenarios, and discuss their identification as sources of deviations in fermion-pair production processes at the International Linear Collider, if they were observed. We emphasize the role of e^- and e^+ polarization in enhancing the identification reaches.

hep-ph↗
arXiv2006

Discriminating large extra dimensions at the ILC with polarized beams

Non-standard scenarios described by effective interactions can manifest themselves indirectly, via corrections to the Standard Model cross sections. It should be desirable to identify at a given confidence level the source of such deviations among the different possible explanations. We here discuss the identification reach on gravity in extra dimensions from the four-fermion compositeness-inspired contact interactions and viceversa, using as basic observable the differential cross section of $e^+e^-\to\bar{f}f$ at the ILC, and emphasize the role of beams polarization in enhancing the identification sensitivity.

hep-ph↗
arXiv2005

Distinguishing New Physics Scenarios at a Linear Collider with Polarized Beams

Numerous non-standard dynamics are described by contact-like effective interactions that can manifest themselves through deviations of the cross sections from the Standard Model predictions. If one such deviation were observed, one should try to identify to a given confidence level the actual source among the possible non-standard interactions that in principle can explain it. We here estimate the potential identification reach on different New Physics effective interactions, obtainable from the angular distributions of lepton pair production processes at the planned International Linear Collider with polarized beams. The models discussed are the interactions based on gravity in large and in TeV^{-1} extra dimensions and the compositeness-inspired four-fermion contact interactions. The availability of both beams polarized in many cases plays an essential role in enhancing the identification sensitivity.

hep-ph↗
arXiv2005

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. For typical c.m. energies and time-integrated luminosities foreseen at the International Linear Collider [\sqrt s=0.5-1 TeV, L_{int}=50-1000 fb^{-1}], a 5σidentification reach as high as 3.5-5.8 TeV for the mass scale M_H relevant to the ADD model can be obtained, while the size of the reach on the mass scales Lambda characterizing four-fermion contact interactions can be of the order of 45-65 TeV.

hep-ph↗
arXiv2005

The role of polarized positrons and electrons in revealing fundamental interactions at the Linear Collider

The proposed International Linear Collider (ILC) is well-suited for discovering physics beyond the Standard Model and for precisely unraveling the structure of the underlying physics. The physics return can be maximized by the use of polarized beams. This report shows the paramount role of polarized beams and summarizes the benefits obtained from polarizing the positron beam, as well as the electron beam. The physics case for this option is illustrated explicitly by analyzing reference reactions in different physics scenarios. The results show that positron polarization, combined with the clean experimental environment provided by the linear collider, allows to improve strongly the potential of searches for new particles and the identification of their dynamics, which opens the road to resolve shortcomings of the Standard Model. The report also presents an overview of possible designs for polarizing both beams at the ILC, as well as for measuring their polarization.

hep-ph↗
arXiv2005

Study of multiparticle production by gluon dominance model (Part II)

The gluon dominance model presents a description of multiparticle production in proton-proton collisions and proton-antiproton annihilation. The collective behavior of secondary particles in $pp$-interactions at 70 GeV/c and higher is studied in the project {\bf "Thermalization"}. The obtained neutral and charged multiplicity distribution parameters explain some RHIC-data. The gluon dominance model is modified by the inclusion of intermediate quark topology for the multiplicity distribution description in the pure $p\bar p$-annihilation at few tens GeV/c and explains behavior of the second correlative moment. This article proposes a mechanism of the soft photon production as a sign of hadronization. Excess of soft photons allows one to estimate the emission region size.

hep-ph↗
arXiv2005

Identification of indirect new physics effects at e^+e^- colliders: the large extra dimensions case

We discuss indirect manifestations of graviton exchange, predicted by large extra dimensions, in fermion-pair production at a high-energy e^+e^- collider. By means of specifically defined asymmetries among integrated angular distributions, the graviton exchange signal can be cleanly distinguished from the effects of either vector-vector contact interactions or heavy scalar exchanges. The role of initial electron and positron beams polarization is also discussed. The method is applied to a quantitative assessment of the sensitivity to the mass cut-off parameter M_H of the KK graviton tower in the ADD scenario, and of the potential identification reach of this mechanism obtainable at the currently planned Linear Collider.

hep-ph↗
arXiv2004

Search and identification of extra spatial dimensions at LHC

We present an analysis, based on the center-edge asymmetry, to distinguish effects of extra dimensions within the Arkani-Hamed-Dimopoulos-Dvali (ADD) and Randall-Sundrum (RS) scenarios from other new physics effects in lepton-pair production at the CERN Large Hadron Collider LHC. Spin-2 and spin-1 exchange can be distinguished up to an ADD cutoff scale, M_H, of about 5 TeV, at the 95% CL. In the RS scenario, spin-2 resonances can be identified in most of the favored parameter space.

hep-ph↗
arXiv2004

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 ADD and RS scenarios. At the Tevatron, the graviton-Z interference is the most important contribution to the center-edge asymmetry, whereas at the LHC, the dominant contribution comes from gluon fusion via graviton exchange, which has no analogue at e^+ e^- colliders. We find that spin-2 and spin-1 exchange can be distinguished up to an ADD cut-off scale, M_H, of about 5 TeV, at the 95% CL. In the RS scenario, spin-2 resonances can be identified in most of the favored parameter space.

hep-ph↗
arXiv2004

Model-independent analysis of four-fermion contact interaction at e^+e^- collider

We study electron-electron contact-interaction searches in the process e^+e^-\to e^+e^- at a future e^+e^- Linear Collider with both beams longitudinally polarized. We evaluate the model-independent constraints on the coupling constants, emphasizing the role of beam polarization, and make a comparison with the case of e^+e^-\toμ^+μ^-.

hep-ph↗
arXiv2003

Discriminating graviton exchange effects from other new physics scenarios in e^+e^- collisions

We study the possibility of uniquely identifying the effects of graviton exchange from other new physics in high energy e^+e^- annihilation into fermion-pairs. For this purpose, we use as basic observable a specific asymmetry among integrated differential distributions, that seems particularly suitable to directly test for such gravitational effects in the data analysis.

hep-ph↗
arXiv2003

Model-independent constraints on contact interactions from LEP2 data analysis

We derive model-independent constraints on four-fermion contact interaction-type dynamics from the published preliminary LEP2 experimental data on e^+e^- annihilation into μ^+μ^- and τ^+τ^- pairs, measured at different energies between 130 and 207 GeV. The basic observables are chosen to be the total cross section and the forward-backward asymmetry, and the analysis realistically takes into account data uncertainties and correlations among measurements at the various energies. The combination of data from different energy points plays an important role in the determination of regions allowed for the contact interaction coupling constants. In contrast to the more common one-parameter analyses, we only obtain constraints on pairs of parameters rather than limits on individual ones.

hep-ph↗
arXiv2002

Bhabha vs. Moller scattering as a contact-interaction analyzer at a polarized Linear Collider

We discuss electron-electron contact-interaction searches in the Bhabha and Moller processes at planned Linear Colliders run in the electron-positron and electron-electron modes, with longitudinally polarized beams. Our analysis is based on the measurement, for the two processes, of polarized differential cross sections that allow to disentangle the different, independent, four-fermion couplings. We evaluate by a model-independent analysis the sensitivities to the contact coupling constants, emphasizing the role of the available beam polarization and the complementarity of the two processes in giving the best limits. We also make a comparison with the potential of $e^+e^-\toμ^+μ^-$ at the same energy and beams polarization.

hep-ph↗