Renormalization Group Equation and QCD Coupling Constant in the Presence of SU(3) Chromo-Electric Field

We solve renormalization group equation in QCD in the presence of SU(3) constant chromo-electric field E^a with arbitrary color index a=1,2,...8 and find that the QCD coupling constant \alpha_s depends on two independent casimir/gauge invariants C_1=[E^aE^a] and C_2=[d_{abc}E^aE^bE^c]^2 instead of one gauge invariant C_1=[E^aE^a]. The \beta function is derived from the one-loop effective action. This coupling constant may be useful to study hadron formation from color flux tubes/strings at high energy colliders and to study quark-gluon plasma formation at RHIC and LHC.Comment: 13 pages latex, 4 eps figs, Eur. Phys. J.

New results in the deformed N=4 SYM theory

We investigate various perturbative properties of the deformed N=4 SYM theory. We carry out a three-loops calculation of the chiral matter superfield propagator and derive the condition on the couplings for maintaining finiteness at this order. We compute the 2-, 3- and 4-point functions of composite operators of dimension 2 at two loops. We identify all the scalar operators (chiral and non-chiral) of bare dimension 4 with vanishing one-loop anomalous dimension. We compute some 2- and 3-point functions of these operators at two loops and argue that the observed finite corrections cannot be absorbed by a finite renormalization of the operators.Comment: LaTeX, 16 pages, 1 figure; references added; typos corrected; final version to appear in Nucl. Phys.

On the possibility of a very light A^0 at low \tan\beta

The searches at LEP II for the processes e^+e^-\to h^0Z and e^+e^-\to h^0A^0 in the Minimal Supersymmetric Standard Model (MSSM) fail to exclude regions of the m_h,m_A plane where \tan\beta <1, thus allowing a very light A^0 (m_A< 20 GeV). Such a parameter choice would predict a light H^\pm with m_{H^\pm}< m_W. Although the potentially large branching ratio for H^\pm \to A^0 W^* would ensure that H^\pm also escaped detection in direct searches at LEP II and the Tevatron Run I, we show that this elusive parameter space is overwhelmingly disfavoured by electroweak precision measurements.Comment: 11 pages, 2 figures, Revtex, references added, minor additions to tex

Schwinger Mechanism for Gluon Pair Production in the Presence of Arbitrary Time Dependent Chromo-Electric Field

We study Schwinger mechanism for gluon pair production in the presence of arbitrary time-dependent chromo-electric background field $E^a(t)$ with arbitrary color index $a$=1,2,...8 in SU(3) by directly evaluating the path integral. We obtain an exact expression for the probability of non-perturbative gluon pair production per unit time per unit volume and per unit transverse momentum $\frac{dW}{d^4x d^2p_T}$ from arbitrary $E^a(t)$. We show that the tadpole (or single gluon) effective action does not contribute to the non-perturbative gluon pair production rate $\frac{dW}{d^4x d^2p_T}$. We find that the exact result for non-perturbative gluon pair production is independent of all the time derivatives $\frac{d^nE^a(t)}{dt^n}$ where $n=1,2,....\infty$ and 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: $E^a \to E^a(t)$. This result may be relevant to study the production of a non-perturbative quark-gluon plasma at RHIC and LHC.Comment: 13 pages latex, Published in European Physical Journal

Phenomenological implications of light stop and higgsinos

We examine the phenomenological implications of light $\tilde{t}_R$ and higgsinos in the Minimal Supersymmetric Standard Model, assuming $\tan^2 \beta < m_t / m_b$ and heavy $\tilde{t}_L$ and gauginos. In this simplified setting, we study the contributions to $\Delta m_{B_d}$, $\epsilon_K$, $BR(b \rightarrow s \gamma)$, $R_b \equiv \Gamma (Z \rightarrow b \overline{b}) / \Gamma ( Z \to {\rm hadrons})$, $BR(t \to b W)$, and their interplay.Comment: plain LATEX, 6 figures, 23 A4 page

On the all-order perturbative finiteness of the deformed N=4 SYM theory

We prove that the chiral propagator of the deformed N=4 SYM theory can be made finite to all orders in perturbation theory for any complex value of the deformation parameter. For any such value the set of finite deformed theories can be parametrized by a whole complex function of the coupling constant g. We reveal a new protection mechanism for chiral operators of dimension three. These are obtained by differentiating the Lagrangian with respect to the independent coupling constants. A particular combination of them is a CPO involving only chiral matter. Its all-order form is derived directly from the finiteness condition. The procedure is confirmed perturbatively through order g^6.Comment: LaTeX, 28 pages, 5 figure

Charge Form Factor and Cluster Structure of 6^6Li Nucleus

The charge form factor of ${}^6$Li nucleus is considered on the basis of its cluster structure. The charge density of ${}^6$Li is presented as a superposition of two terms. One of them is a folded density and the second one is a sum of ${}^4$He and the deuteron densities. Using the available experimental data for ${}^4$He and deuteron charge form factors, a good agreement of the calculations within the suggested scheme is obtained with the experimental data for the charge form factor of ${}^6$Li, including those in the region of large transferred momenta.Comment: 12 pages 5 figure

Event Shape/Energy Flow Correlations

We introduce a set of correlations between energy flow and event shapes that are sensitive to the flow of color at short distances in jet events. These correlations are formulated for a general set of event shapes, which includes jet broadening and thrust as special cases. We illustrate the method for electron-positron annihilation dijet events, and calculate the correlation at leading logarithm in the energy flow and at next-to-leading-logarithm in the event shape.Comment: 43 pages, eight eps figures; minor changes, references adde

String-localized Quantum Fields and Modular Localization

We study free, covariant, quantum (Bose) fields that are associated with irreducible representations of the Poincar\'e group and localized in semi-infinite strings extending to spacelike infinity. Among these are fields that generate the irreducible representations of mass zero and infinite spin that are known to be incompatible with point-like localized fields. For the massive representation and the massless representations of finite helicity, all string-localized free fields can be written as an integral, along the string, of point-localized tensor or spinor fields. As a special case we discuss the string-localized vector fields associated with the point-like electromagnetic field and their relation to the axial gauge condition in the usual setting.Comment: minor correction

New hadrons as ultra-high energy cosmic rays

Ultra-high energy cosmic ray (UHECR) protons produced by uniformly distributed astrophysical sources contradict the energy spectrum measured by both the AGASA and HiRes experiments, assuming the small scale clustering of UHECR observed by AGASA is caused by point-like sources. In that case, the small number of sources leads to a sharp exponential cutoff at the energy E<10^{20} eV in the UHECR spectrum. New hadrons with mass 1.5-3 GeV can solve this cutoff problem. For the first time we discuss the production of such hadrons in proton collisions with infrared/optical photons in astrophysical sources. This production mechanism, in contrast to proton-proton collisions, requires the acceleration of protons only to energies E<10^{21} eV. The diffuse gamma-ray and neutrino fluxes in this model obey all existing experimental limits. We predict large UHE neutrino fluxes well above the sensitivity of the next generation of high-energy neutrino experiments. As an example we study hadrons containing a light bottom squark. These models can be tested by accelerator experiments, UHECR observatories and neutrino telescopes.Comment: 17 pages, revtex style; v2: shortened, as to appear in PR