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Shmuel Nussinov

Publications and source records attributed to Shmuel Nussinov.

At least 73 records · Page 4Linked to original sources
arXiv2004

Production of the X(3872) in B Meson Decay by the Coalescence of Charm Mesons

If the recently-discovered charmonium state X(3872) is a loosely-bound S-wave molecule of the charm mesons \bar D^0 D^{*0} or \bar D^{*0} D^0, it can be produced in B meson decay by the coalescence of charm mesons. If this coalescence mechanism dominates, the ratio of the differential rate for B^+ \to \bar D^0 D^{*0} K^+ near the \bar D^0 D^{*0} threshold and the rate for B^+ \to X K^+ is a function of the \bar D^0 D^{*0} invariant mass and hadron masses only. The identification of the X(3872) as a \bar D^0 D^{*0}/\bar D^{*0} D^0 molecule can be confirmed by observing an enhancement in the \bar D^0 D^{*0} invariant mass distribution near the threshold. An estimate of the branching fraction for B^+ \to X K^+ is consistent with observations if X has quantum numbers J^{PC} = 1^{++} and if J/ψπ^+ π^- is one of its major decay modes.

hep-ph↗
arXiv2004

"Atmospheric Neutrino" and "Proton Decay" Data Exclude Some New Dark Matter Scenarios

Models in which the "dark" halo particles have mutual and potentially also appreciable nuclear interactions have been considered by various authors. In this note we briefly point out strategies for a most sensitive search for these particles. We show that a particular matter/anti-matter symmetric variant due to Farrar et al. is excluded by combining bounds on proton decay from various experiments and from super-Kamiokande and atmospheric neutrino measurements at super-Kamiokande.

hep-ph↗
arXiv2004

Are Bulk Axions in Models with Extra, Large, Compact Dimensions Observable?

The high degeneracy of KK modes in models which have bulk axions moving in some extra, compact dimensions which are larger than O (Angstrom)strongly tightens the supernova upper bounds on the axion photon coupling making axions practically unobservable. Conversely, discovering axions directly or indirectly will exclude such models. These drastic conclusions are avoided if the supernova and bounds from solar axion searches are relaxed.

hep-ph↗
arXiv2004

Some (further) Comments on the Theta(1540) Pentaquark

Additional broader I=0 states in the KN channel near $Θ^+$(1540) are expected in many models, making the absence of any signature in the K$^+$-deuteron scattering data even more puzzling. In an ideal "three-body" picture the $Θ$ is viewed as two compact ud(1)ud(2) $\bar{3}$ color diquarks and an $\bar{s}$ quark. A "QCD-type" inequality involving $m(Θ^+), m(Λ)$, the mass of the $Λ(1/2^-) $ L=1 excitation and that of a new I=0 tetraquark vector meson then follows. The inequality suggests a very light new vector meson, and is violated. We note that "associated production" of the pentaquark with another quadriquark or anti-pentaquark may be favored. This along with some estimates of the actual production cross sections suggest that the $Θ$ can be found in BaBar or Belle e$^+$-e$^-$ colliders.

hep-ph↗
arXiv2003

The Narrow Theta(1543)--A QCD Dilemma: Tube or Not Tube?

We argue that a width of less than MeV of the new Theta resonance is inconsistent with the observed ratio of resonance and background events in the various photon initiated experiments if the latter can be described by K, K*, etc., exchange. An evaluation of the Feynman diagrams which were believed to be relevant is presented and supports the general claim in the one case where a cross section has been given by the experimental group. More detailed arguments based on the flux tube model explaining the narrow widths and the apparent conflict with the production rates are presented. We predict narrow Tetra-quarks at mass ~ O(1-1.2 GeV) which the analysis of LEAR may have missed.

hep-ph↗
arXiv2003

New near-threshold mesons

We show that under a number of rather plausible assumptions QCD spectrum may contain a number of mesons which have not been predicted or observed. Such states will have the quantum numbers of two existing mesons and masses very close to the dissociation threshold into the two mesons. Moreover, at least one of the two mesonic constituents itself must be very close to its dissociation threshold. In particular, one might expect the existence of loosely bound systems of $D$ and $\D$; similarly, $K$ and $\ff$, $\bar{K}$ and $\ff$, $K$ and $å$ and $\bar{K}$ and $å$ can be bound. The mechanism for binding in these cases is the S-wave kaon exchange. The nearness of one of the constituents to its decay threshold into a kaon plus a remainder, implies that the range of the kaon exchange force becomes abnormally long--significantly longer than $1/m_K$ which greatly aids the binding.

hep-ph↗
arXiv2002

Does A Narrow Tetraquark $cc\bar{u}\bar{d}$ State Exist?

The existence of a shallow or virtual tetraquark state, $cc\bar{u}\bar{d}$, is discussed. Using the putative masses for the doubly charmed baryons ($ccu/ccd$) from SELEX, the mass of the $cc\bar{u}\bar{d}$ state is estimated to be about $3.9 GeV$, only slightly above the $DD^*$ threshold. The experimental signatures for various $cc\bar{u}\bar{d}$ masses are also discussed.

hep-ph↗
arXiv2002

A Novel Approach Applied to the Largest Clique Problem

A novel approach to complex problems has been previously applied to graph classification and the graph equivalence problem. Here we apply it to the NP complete problem of finding the largest perfect clique within a graph $G$.

cond-mat↗
arXiv2002

A Novel Approach to Complex Problems

A novel approach to complex problems has been previously applied to graph classification and the graph equivalence problem. Here we consider its applications to a wide set of NP complete problems, namely, those of finding a subgraph g inside a graph G.

cond-mat.dis-nn↗
arXiv2002

Approaches to Network Classification

We introduce a novel approach to description of networks/graphs. It is based on an analogue physical model which is dynamically evolved. This evolution depends on the connectivity matrix and readily brings out many qualitative features of the graph.

cond-mat.stat-mech↗
arXiv2002

Experimental identification of non-pointlike dark-matter candidates

We show that direct dark matter detection experiments can distinguish between pointlike and non-pointlike dark-matter candidates. The shape of the nuclear recoil energy spectrum from pointlike dark-matter particles, e.g., neutralinos, is determined by the velocity distribution of dark matter in the galactic halo and by nuclear form factors. In contrast, typical cross sections of non-pointlike dark matter, for example, Q-balls, have a new form factor, which decreases rapidly with the recoil energy. Therefore, a signal from non-pointlike dark matter is expected to peak near the experimental threshold and to fall off rapidly at higher energies. Although the width of the signal is practically independent of the dark matter velocity dispersion, its height is expected to exhibit an annual modulation due to the changes in the dark matter flux.

hep-ph↗
arXiv2002

QCD and e+e- --> Baryon + anti-Baryon

We discuss the QCD constraints on e+e- --> baryon-anti-baryon close to threshold, in light of the puzzling experimental data which indicate that close to threshold sigma (e+e- --> n n-bar) > sigma (e+e- --> p p-bar). We focus on the process e+e- --> Delta Delta-bar, which is particularly simple from the theoretical point of view. In this case it is possible to make exact QCD predictions for the relative yields of the four members of the Delta multiplet, modulo one crucial dynamical assumption.

hep-ph↗
arXiv2001

n-nbar Oscillations in Models with Large Extra Dimensions

We analyze $n - \bar n$ oscillations in generic models with large extra dimensions in which standard-model fields propagate and fermion wavefunctions have strong localization. We find that in these models $n - \bar n$ oscillations might occur at levels not too far below the current limit.

hep-ph↗
arXiv2001

Expected Signals in Relic Neutrino Detectors

Here we estimate the magnitude of the signals expected for realistic cosmic neutrino backgrounds in detectors attempting to measure the mechanical forces exerted on macroscopic targets by the elastic scattering of relic neutrinos. We study effects proportional to the weak coupling constant $G_F$ and to $G_F^2$ for Dirac and Majorana neutrinos, either relativistic or non-relativistic, both gravitationally bound or not.

hep-ph↗
arXiv1999

QCD Inequalities

We review the subject of QCD inequalities, using both a Hamiltonian variational approach, and a rigorous Euclidean path integral approach.

hep-ph↗
arXiv1998

Some Remarks on Theories with Large Compact Dimensions and TeV-Scale Quantum Gravity

We comment on some implications of theories with large compactification radii and TeV-scale quantum gravity. These include the behavior of high-energy gravitational scattering cross sections and consequences for ultra-high-energy cosmic rays and neutrino scattering, the question of how to generate naturally light neutrino masses, the issue of quark-lepton unification, the equivalence principle, and the cosmological constant.

hep-ph↗