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Haim Goldberg

Publications and source records attributed to Haim Goldberg.

87 records · Page 5Linked to original sources

Clustering in Highest Energy Cosmic Rays: Physics or Statistics?

Directional clustering can be expected in cosmic ray observations due to purely statistical fluctuations for sources distributed randomly in the sky. We develop an analytic approach to estimate the probability of random cluster configurations, and use these results to study the strong potential of the HiRes, Auger, Telescope Array and EUSO/OWL/AirWatch facilities for deciding whether any observed clustering is most likely due to non-random sources.

astro-ph↗

Proposal for a Constant Cosmological Constant

It is proposed that the apparent positive acceleration of the cosmological scale factor is due to the vacuum energy of an incomplete chiral phase transition in a hidden SU(2) sector. Constraints from primordial nucleosynthesis imply that the present metastable phase is in a substantially supercooled state. It is argued that massless chiral condensates can substantially enhance the possibility of supercooling, and a linear sigma model exhibiting scale invariance broken only at the quantum level is shown to accommodate the required supercooling with a reasonable choice of quartic couplings. The extensive supercooling can in principle be confirmed or rejected on the basis of interface tension measurements in lattice simulations with dynamical fermions.

hep-ph↗

Leptogenesis and the Small-Angle MSW Solution

The lepton asymmetry created in the out-of-equilibrium decay of a heavy Majorana neutrino can generate the cosmological baryon asymmetry when processed through fast anomalous electroweak reactions. In this work I examine this process under the following assumptions: (1) maximal nu_mu/nu_tau mixing (2) hierarchical mass spectrum m_3 >> m_2 (3) small-angle MSW solution to the solar neutrino deficit. Working in a basis where the charged lepton and heavy neutrino mass matrices are diagonal, I find the following bounds on the heavy Majorana masses M_i: (a) for a symmetric Dirac neutrino mass matrix (no other constraints), an asymmetry compatible with BBN constraints can be obtained for min(M_2,M_3)> 10^{11} GeV; (b) if {\em any} of the Dirac matrix elements vanishes, successful baryogenesis can be effected for a choice of min(M_2,M_3) as low as a few times 10^{9} GeV. The latter is compatible with reheat requirements for supersymmetric cosmologies with sub-TeV gravitino masses.

hep-ph↗

Gravitons and the Drell-Hearn-Gerasimov Sum Rule

One-loop diagrams containing a graviton provide a finite contribution to the anomalous magnetic moment $\al$ of a lepton, whether or not the graviton propagates in $n$ large extra compact dimensions. In the present work, the tree graph photoproduction of a graviton, integrated up to an arbitrary cutoff, is shown to violate the Drell-Hearn-Gerasimov sum rule for $\al^2$. The possibility of resurrecting the sum rule from high energy contributions originating in string excitations is discussed in a qualitative manner, and various problems associated with such a program are pointed out.

hep-ph↗

Lower Energy Consequences of an Anomalous High-Energy Neutrino Cross-Section

A new strong-interaction has been postulated for neutrinos above ~10^{19} eV to explain the production of highest-energy cosmic ray events. We derive a dispersion relation relating the hypothesized high-energy cross-section to the lower-energy neutrino-nucleon elastic amplitude. Remarkably, we find that the real forward amplitude becomes anomalous seven orders of magnitude lower in energy than does the total cross-section. We discuss possible measurable consequences of this early onset of new neutrino physics, and conclude that a significantly enhanced elastic ν-N scattering rate may occur for the neutrino beams available at Fermilab and CERN.

hep-ph↗

Evidence for a Non-Zero Mass in the Dispersion Relation of Transverse Photons in the Stellar Core

The electromagnetic two-body interaction energy is modified in the thermal environment of the solar core. The modifications are shown to imply a gross violation of standard solar physics unless the dispersion relation ω_t(k) for the transverse modes of the photon is altered to include a transverse mass. A non-zero transverse mass $m_t^2\simeq e^2 n_e/m_e$ is, of course, theoretically predicted to exist; the discussion in this paper implies that such a mass is required in order to maintain the success of the standard solar model. In that sense one may claim observational evidence for a non-trivial dispersion relation for transverse photon frequencies in the solar core.

hep-ph↗

From Planck to GUT via Dimensional Transmutation

Consider a gauge singlet superfield S coupled to a pair of adjoint fields in a SUSY-GUT. If the tree-level vacuum is flat in S, the vev which defines the GUT scale will be determined via dimensional transmutation at a scale M where the soft-breaking (mass)^2 vanishes as a result of running from $M_{Pl} = (8 πG_N)^{-1/2}$. Because of the large number of adjoint fields $N_A$ coupled to S, one finds that M can be generically close to $M_{GUT} = 2 \times 10^{16} GeV$: $M \simeq M_{Pl} \exp[-16 π^2 \log(3/2) / (N_A+4) λ^2]$, where $λ$ is a Yukawa $\sim$ 0.7. This work examines the symmetries and dynamical constraints required in a SUSY-GUT in order that the desired flatness in S is achieved, and that this flatness may survive in a supergravity framework.

hep-ph↗

Thermodynamics of Hidden Sector Gaugino Condensation in the Expanding Universe

This work examines the confining-deconfining phase transition in a hidden Yang Mills sector with scale $Λ\sim 10^{14}$ GeV appropriate to dilaton stabilization and SUSY-breaking via formation of a gaugino consensate. If the transition is assumed to take place through homogenous nucleation, then under reasonable assumptions it is found that a critical bubble, formed at a temperature which provides enough supercooling, is not large enough to accommodate an adequate number $(\gsim 100)$ of quanta of the confined phase (`hidden hadrons') to allow a consistent thermodynamic description. Thus, a first order transition in the hidden sector may not be possible in the expanding universe.

hep-ph↗

How Georgi-Jarlskog and SUSY-SO(10) imply a measurable rate for mu->e gamma

Slepton mass matrices have been analyzed in an SO(10) SUSY-GUT, with soft-breaking terms generated at Planck scale. Higher dimensional operators consistent with 4-d string constructions are used in order to generate a Georgi-Jarlskog (G-J) Yukawa texture at \mgut. Radiative corrections between \mpl\ and \mgut\ generate a substantial non-universality in the $\tildeμ-\tilde e$ sector. This non-universality originates in the flavor dependence of the Higgs assignments required for the G-J texture, and is unrelated to the large top Yukawa. The resulting branching ratio for mu->e could make this process observable for large sectors of the MSSM parameter space, with a factor of 10 improvement in statistics.

hep-ph↗

Lepton Flavor Violation in SUSY-SO(10) with Predictive Yukawa Texture

We analyze the scalar lepton mass matrices in a supersymmetric SO(10) grand unified model with soft SUSY breaking terms generated at Planck scale and a Georgi-Jarslkog Yukawa texture at GUT scale induced by higher dimensional operators. This model predicts lepton flavor violation. The predictive features of the Georgi-Jarlskog texture are used to estimate branching ratios for the radiative decays $e_{a} \rightarrow e_{b}+γ,$ and we find rates that could provide an experimental test for this kind of model.

hep-ph↗

Can Hidden Gauginos Form Condensates?

Supersymmetry breaking may be linked to the formation of gaugino condensates in a hidden sector. In this work, the process of formation of the condensate is examined in a cosmological context, using an effective field theory of the gaugino bilinear which provides a reasonable interpolation between the high- and low-temperature phases. The implementation of anomaly requirements generates a large potential barrier between the zero-condensate configuration and that of the true (SUSY-breaking) vacuum. As a consequence, the transition to bubbles of true vacuum may be subject to an enormous exponential suppression. This leads to the same difficulties with inhomogeneity of the universe which occurred in the original inflationary scenarios.

hep-th↗

The Mass of the Dilaton

It is shown that, in a theory where the dilaton is coupled to a Yang-Mills gauge field which enters a confining phase at scale Λ, the dilaton may grow a mass $m_{dilaton}\sim Λ^2/m_{Pl}\sim (m_{SUSY}^2 m_{Pl})^{1/3}\sim 10^8\ \mbox{GeV}. $ This allows ample time for decay before the electroweak era if $m_{SUSY}\simeq 1\ \mbox{TeV},$ and circumvents cosmological problems normally associated with its existence.

hep-ph↗

Gaugino Condensation as the Origin of Primordial Fluctuations

I present a model for inflation based on the gaugino-dilaton dynamics of supersymmetry breaking. The inflaton is the dimension--1 scalar field $ϕ$ related to the gaugino condensate via $λ^Tλ=ϕ^3.$ Recent work in this area is used to obtain two significant results: (1) Scalar density fluctuations at second horizon crossing are generated on scale $λ$ with amplitude \[ \drr=A\cdot \ 10^3\cdot\ \left(\frac{m_{SUSY}}{m_{Pl}}\right)^{\half}\ \left(\fracλ{100\ \mbox{Mpc}}\right)^{0.03}\ \ , \] where $A$ is a constant which depends on (unknown) details of gaugino-dilaton dynamics in the strong-coupling phase. Agreement with COBE results is obtained if $A\simeq 2.$ \ (2) Due to mixing with hidden sector glueballs, the dilaton mass is large $(\sim \left(\mp\ \ms^2\right)^ {\frac{1}{3}}\sim 10^8\ \mbox{GeV}),$ and reheating takes place at $T\sim 1\tev.$ This {\em necessitates} that the presently observed baryon asymmetry be generated at a cosmic temperature below 1 TeV.

hep-ph↗

Large Multiplicity Gluon Production in QCD

We compute the approximate cross section $σ_n^{(0)}$ for producing $n-2$ {\it resolved} gluons in a gluon-gluon collision, using the Parke-Taylor formula regularized in a Lorentz invariant manner. We find, in double leading logarithm approximation, that \[ σ_{n}^{(0)} \approx \frac{1}{s} \left( \frac{N_cα_s}{2 π\sqrt{12}} \ \ln^{2} (s/s_{cut})\right)^{n-2}\ \ , \] where $\sqrt{s_{cut}}$ is the minimum invariant mass for a resolved gluon pair. There is no factor of $1/(n-2)!$ multiplying the expression. We present additional numerical results, and comment on their implications for perturbative calculations of $n$-jet cross sections at colliders.

hep-ph↗

Exact Nonperturbative Unitary Amplitudes for 1->N Transitions

I present an extension to arbitrary N of a previously proposed field theoretic model, in which unitary amplitudes for $1->8$ processes were obtained. The Born amplitude in this extension has the behavior $A(1->N)^{tree}\ =\ g^{N-1}\ N!$ expected in a bosonic field theory. Unitarity is violated when $|A(1->N)|>1$, or when $N>\N_crit\simeq e/g.$ Numerical solutions of the coupled Schrödinger equations shows that for weak coupling and a large range of $N>\ncrit,$ the exact unitary amplitude is reasonably fit by a factorized expression $|A(1->N)| \sim (0.73 /N) \cdot \exp{(-0.025/\g2)}$. The very small size of the coefficient $1/\g2$ , indicative of a very weak exponential suppression, is not in accord with standard discussions based on saddle point analysis, which give a coefficient $\sim 1.\ $ The weak dependence on $N$ could have experimental implications in theories where the exponential suppression is weak (as in this model). Non-perturbative contributions to few-point correlation functions in this theory would arise at order $K\ \simeq\ \left((0.05/\g2)+ 2\ ln{N}\right)/ \ ln{(1/\g2)}$ in an expansion in powers of $\g2.$

hep-ph↗