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arXiv2007

Spin Effects in Quantum Chromodynamics and Recurrence Lattices with Multi-Site Exchanges

In this thesis, we consider some spin effects in QCD and recurrence lattices with multi-site exchanges. Main topic of our manuscript are critical phenomena in spin systems defined on the recurrence lattices. Main tool of our approach is the method of recursive (hierarchical) lattices. We apply the method of dynamical mapping (or recursive lattices) for investigation of magnetic properties of the fluid and solid $^3$He, phase transitions in crystals and macromolecules. First, we analyze the helix-coil phase transition for polypeptides and proteins, and describe an quasi unfolding transition (like the cold denaturation process) for the degree of helicity (the order parameter for macromolecules). Next we consider the recurrent models of $^3$He defined on the square, Husimi and hexagon lattices. Using the method of dynamical mapping, the magnetization curves with plateaus, bifurcation point and one period doubling are obtained. Then we investigate the model with cubic symmetry defined on the Bethe lattice and containing both linear and quadratic spin-spin interactions. The magnetization of the system is calculated, and a complex structure of the phase transitions between the disordered, partially ordered and completely ordered states is observed. In the framework of QCD, we consider the azimuthal asymmetries in heavy flavor production in the lepton-nucleon deep inelastic scattering (DIS). We calculate the azimuthal (or $ϕ$-) dependence of the next-to-leading order heavy-quark-initiated contributions to DIS. It is shown that, contrary to the basic gluon-initiated component, the photon-quark scattering mechanism is practically $\cos2ϕ$-independent. We investigate the possibility of measuring both nonperturbative (intrinsic) and perturbative (CTEQ, MRST) charm distributions using the $\cos2ϕ$ asymmetry.

cond-mat.stat-mech↗

arXiv2007

Correlations with Photons in Heavy-Ion Collisions

We present a study of two-particle correlation functions involving photons and neutral pions in proton-proton and lead-lead collisions at the LHC energy. The aim is to use these correlation functions to quantify the effects of the medium on the jet decay properties.

hep-ph↗

arXiv2013

SUSY: New Perspectives and Variants

Although supersymmetry (SUSY) is thirty five years old, it is still one of the most attractive theories for physics beyond the standard model. Assuming that SUSY will be discovered at the LHC, the key question is: What SUSY model do we expect to be the correct one ? After reviewing briefly the advantages and problems of SUSY, several interesting models that have been proposed in the literature will be discussed. In particular, models such as the MSSM, BRpV, NMSSM, and possible extensions. We will also introduce the $μ\nuSSM$ whose interest resides in the fact that it generates a solution to the (famous) $μ$ problem of SUSY models that is connected to the (nowadays very popular) neutrino physics.

hep-ph↗

arXiv2007

|V_{ub}| from the Spectrum of B->pi e nu

I discuss the results for $|V_{ub}|f_+(0)$ and $|V_{ub}|$ obtained from the spectrum of $B\toπe ν$ and the form factor $f_+(q^2)$ from QCD sum rules on the light-cone and unquenched lattice calculations; the shape of $f_+(q^2)$ is fixed from experimental data.

hep-ph↗

arXiv2007

New Physics with Tagged Forward Protons at the LHC

The addition of forward proton detectors to LHC experiments will significantly enlarge the potential for studying New Physics. A topical example is Higgs production by the central exclusive diffractive process, pp -> p+H+p. We discuss the exclusive production of Higgs bosons in both the SM and MSSM. Special attention is paid to the backgrounds to the H -> bbbar signal.

hep-ph↗

arXiv2007

Accurate backgrounds to Higgs production at the LHC

Corrections of 10-30% for backgrounds to the H --> WW --> l^+l^-\sla{p}_T search in vector boson and gluon fusion at the LHC are reviewed to make the case for precise and accurate theoretical background predictions.

hep-ph↗

arXiv2007

Kaon semileptonic decay (K_{l3}) form factor in the nonlocal chiral quark model

We investigate the kaon semileptonic decay (K_{l3}) form factors within the framework of the nonlocal chiral quark model from the instanton vacuum, taking into account the effects of flavor SU(3) symmetry breaking. All theoretical calculations are carried out without any adjustable parameter. We also show that the present results satisfy the Callan-Treiman low-energy theorem as well as the Ademollo-Gatto theorem. It turns out that the effects of flavor SU(3) symmetry breaking are essential in reproducing the kaon semileptonic form factors. The present results are in a good agreement with experiments, and are compatible with other model calculations.

hep-ph↗

arXiv2007

Note on color neutral solutions of the $K^0$ condensed color-flavor locked phase

In the presence of nonzero strange quark mass $m_s$, we investigate color neutrality in the $K^0$ condensed phase of color-flavor locked quark matter. By treating the $m_s$ effects on both kaon condensate and Fermi-surface phenomenon self-consistently, we develop a new treatment to evaluate color neutral solutions within the model-independent framework. It is pointed out that, in the general sense, the expectation values of gluon fields obtained from dynamics of Goldstone bosons solely are not identified with the factual color chemical potentials.

hep-ph↗

arXiv2007

Unparticle physics in e^+ e^- annihilation

In the recent past,unparticle physics effects have been explored in detail in both the fermionic and bosonic sectors. We have used fermionic unparticles to study the cross-section of electron-positron annihilation to light pseudo-scalar meson pairs e^+e^- ->PP. We show that this cross-section is sensitive to the scaling dimension d_U<1.4.

hep-ph↗

arXiv2011

Schwinger Mechanism for Quark-Antiquark Production in the Presence of Arbitrary Time Dependent Chromo-Electric Field

We study the Schwinger mechanism in QCD in the presence of an arbitrary time-dependent chromo-electric background field $E^a(t)$ with arbitrary color index $a$=1,2,...8 in SU(3). We obtain an exact result for the non-perturbative quark (antiquark) production from an arbitrary $E^a(t)$ by directly evaluating the path integral. We find that the exact result is independent of all the time derivatives $\frac{d^nE^a(t)}{dt^n}$ where $n=1,2,...\infty$. This result has the same functional dependence on two Casimir invariants $[E^a(t)E^a(t)]$ and $[d_{abc}E^a(t)E^b(t)E^c(t)]^2$ as the constant chromo-electric field $E^a$ result with the replacement: $E^a \rightarrow E^a(t)$. This result relies crucially on the validity of the shift conjecture, which has not yet been established.

hep-ph↗

arXiv2007

Relations between classical phase-space distributions and Wigner function for multiparticle production processes

The effects of interpreting classical phase space distributions as Wigner functions, which is common in models of multiparticle production, are discussed. The temperature for the classical description is always higher than that for its Wigner function interpretation. A rough estimate shows that the corresponding correction is proportional to R^(-2), where R is the radius of the interaction region, and that it is negligible for heavy ion scattering, but at the few percent level for e^+e^- annihilations.

hep-ph↗

arXiv2007

Fine-Tuning in Brane-antibrane Inflation

I give a brief overview of brane-antibrane inflation, with emphasis on the problems of tuning to get a flat potential in the KKLMMT framework, and recent work on the nature of superpotential corrections in that model.

hep-th↗

arXiv2008

Higher order QCD corrections in exclusive charmless B decays

We discuss exclusive charmless B decays within the Standard Model of particle physics. In particular, we consider hadronic two-body decays as B -> pi pi and perform a conceptual analysis of heavy-to-light form factors which encode the strong interaction effects in semi-leptonic decays as B -> pi l nu. Concerning the hadronic decays we compute NNLO QCD corrections which are particularly important with respect to strong interaction phases and hence direct CP asymmetries. We present results for the imaginary part of the topological tree amplitudes and a partial calculation of the real part of the amplitudes which is technically more involved. In our conceptual analysis of the QCD dynamics in heavy-to-light transitions we consider form factors between non-relativistic bound states. We perform a NLO analysis and compute the so-called soft-overlap contribution which is calculable in our set-up. As a byproduct of our analysis, we calculate leading-twist light-cone distribution amplitudes for non-relativistic bound states which can be applied for B_c or eta_c mesons.

hep-ph↗

arXiv2007

Tevatron-for-LHC Report: Top and Electroweak Physics

The top quark and electroweak bosons (W and Z) represent the most massive fundamental particles yet discovered, and as such refer directly to the Standard Model's greatest remaining mystery: the mechanism by which all particles gained mass. This report summarizes the work done within the top-ew group of the Tevatron-for-LHC workshop. It represents a collection of both Tevatron results, and LHC predictions. The hope is that by considering and comparing both machines, the LHC program can be improved and aided by knowledge from the Tevatron, and that particle physics as a whole can be enriched. The report includes measurements of the top quark mass, searches for single top quark production, and physics of the electroweak bosons at hadron colliders.

hep-ph↗

arXiv2007

Neutrino Mass Matrix from Seesaw Mechanism Subjected to Texture Zero and Invariant Under a Cyclic Permutation

We evaluate the predictive power of the neutrino mass matrices arising from seesaw mechanism subjected to texture zero and satisfying a cyclic permutation invariant. We found that only two from eight possible patterns of the neutrino mass matrices are invariant under a cyclic permutation. The two resulted neutrino mass matrices which are invariant under a cyclic permutation can be used qualitatively to explain the neutrino mixing phenomena for solar neutrino and to derive the mixing angle that agress with the experimental data.

hep-ph↗

arXiv2007

SUSY Breaking at the Tip of Throat and Mirage Mediation

We discuss some features of supersymmetry breaking induced by a brane-localized source which is stabilized at the IR end of warped throat, and also the resulting mirage mediation pattern of soft terms of the visible fields which are localized in the bulk space corresponding to the UV end of throat. Such supersymmetry breaking scheme can be naturally realized in KKLT-type string compactification, and predicts highly distinctive pattern of low energy superparticle masses which might be tested at the LHC.

hep-th↗

arXiv2007

Final State Interaction Effects in Semi-inclusive Deep Inelastic processes A(e,e'p)X off the deuteron and complex nuclei

The effects of the final state interaction (FSI) in semi inclusive deep inelastic electron scattering processes $A(e,e'p)X$ off nuclei are investigated in details. Proton production is described within the spectator and the target fragmentation mechanisms whose relevance to the experimental study of the deep inelastic structure functions of bound nucleons and the non perturbative hadronization process is analyzed. Particular attention is paid to the deuteron target within kinematical conditions corresponding to the available and forthcoming experimental data at Jlab. We argue that there are kinematical regions where FSI effects are minimized, allowing for a reliable investigation of the DIS structure functions, and regions where the interaction of the quark-gluon debris with nucleons is maximized, which makes it possible to study hadronization mechanisms. Nuclear structure has been described by means of realistic wave functions and spectral functions and the final state interaction has been treated within an eikonal approximation approach which takes into account the rescattering of the quark-gluon debris with the residual nucleus and, in the case of complex nuclei, within an optical potential approach to account for the FSI of the struck proton.

nucl-th↗

arXiv2007

Heavy chiral bosons search at hadron colliders

The production of new spin-1 chiral bosons at the hadron colliders, the Fermilab Tevatron and the CERN LHC, is considered. The masses of the chiral bosons can be determined on the basis of experimental data of precise low-energy experiments, which already indicate indirectly their existence. They can explain, for example, the serious 4.5 sigma discrepancy between the measured and the predicted two pion branching ratio of the tau decay and the sign of the 3.3 sigma deviation of the muon (g-2) theoretical prediction from the experimental value. Quantitative evaluations of the various differential cross-sections of the chiral boson production at hadron colliders are made using the CalcHEP package. It is noteworthy that the Tevatron data already hint the existence of the lightest charged chiral boson with a mass around 500 GeV. New Tevatron data and the LHC results will definitely confirm or reject this indication. In the positive case the LHC would be able to discover all predicted charged and neutral chiral bosons spanning in mass up to 1 TeV.

hep-ph↗