Search

We discuss some implications of models with large extra dimensions, including effects on scattering cross sections, fermion masses and mixings, [Formula: see text] oscillations, and ideas on "half-strings".

We consider models that generate hierarchies via the separation of fermion wavefunctions in higher-dimensional spaces. We calculate the effects of gauge interactions between fermions and show that these are important and could help to explain (i) why the heaviest known fermion is a charge 2/3 quark, rather than a charge -1/3 quark or a lepton, (ii) why this fermion has a mass $m_t$ comparable to the electroweak symmetry breaking scale $M_{ew}$, (iii) the patterns $m_t >> m_b > m_\tau$ and $m_c >> m_s > m_\mu$, and (iv) the smallness of neutrino masses.

Mirror matter models have been suggested recently as an explanation of neutrino puzzles and microlensing anomalies. We show that mirror supernovae can be a copious source of energetic gamma rays if one assumes that the quantum gravity scale is in the TeV range. We show that under certain assumptions plausible in the mirror models, the gamma energies could be degraded to the 10 MeV range (and perhaps even further) so as to provide an explanation of observed gamma ray bursts. This mechanism for the origin of the gamma ray bursts has the advantage that it neatly avoids the ``baryon load problem''., Comment: Latex 8 pages; no figures; UMD-PP-00-024

Oak Ridge National Laboratory, Tennessee, USA, ORLaND is a collaboration proposing a major neutrino physics facility at the Spallation Neutrino Source (SNS) at the Oak Ridge National Laboratory. An underground bunker is proposed adjacent to the first target station of the SNS. The bunker is designed to house one large detector (2000 t) and a number of smaller (200 t) detectors. A comprehensive program of neutrino experiments is being developed that could span the lifetime of the Spallation Source.

We use an Adler–Weisberger sum rule to establish an upper bound Γ(D ∗+ →Dπ)≤270 keV and motivate by various considerations the estimate Γ(D ∗+ →Dπ)≈100 keV.

We suggest scattering experiments which implement the concept of “protective measurements” allowing the measurement of the complete wave function even when only one quantum system (rather than an ensemble) is available. Such scattering experiments require massive, slow, projectiles with kinetic energies lower than the first excitation of the system in question. The results of such experiments can have a (probabilistic) distribution (as is the case when the Born approximation for the scattering is valid) or be deterministic (in a semiclassical limit).

We suggest scattering experiments which implement the concept of “protective measurements” allowing the measurement of the complete wave function even when only one quantum system (rather than an ensemble) is available. Such scattering experiments require massive, slow, projectiles with kinetic energies lower than the first excitation of the system in question. The results of such experiments can have a (probabilistic) distribution (as is the case when the Born approximation for the scattering is valid) or be deterministic (in a semiclassical limit).

We present an estimate of certain higher-order corrections to the contribution of the charm triangle loop in the inclusive {bar B}{r_arrow}X{sub s}{gamma} decay rate recently discussed by Voloshin. We find that these corrections are minute and hence the result found by Voloshin, although small, is quite robust. {copyright} {ital 1997} {ital The American Physical Society}

In this letter, we point out that a discovery of very heavy (mF≥few TeV ) fermions at a future collider is possible only under special circumstances. In particular, we argue that such fermions are likely to be accompanied by new gauge interactions.

The continuous spontaneous localization (CSL) model modifies Schrodinger's equation so that the collapse of the state vector is described as a physical process (a special interaction of particles with a universal fluctuating field). A consequence of the model is that an electron in an atom should occasionally get “spontaneously” knocked out of the atom. The CSL ionization rate for the 1s electrons in the Ge atom is calculated and compared with an experimental upper limit for the rate of “spontaneously” generated x-ray pulses in Ge. This gives, for the first time, an experimental constraint on the parameters which characterize this model (the GRW parameters and the relative collapse rate of electrons and nucleons). It is concluded that the values assigned to the GRW parameters by GRW may be maintained only if the coupling of electrons to the fluctuating field is 0.35% or less than the coupling of nucleons, suggestive of a mass-proportional (and therefore gravitational) collapse mechanism. For other allowed values of the GRW parameters, it is still argued that nucleons should collapse more rapidly than electrons.

We examine the implications of the hypothesis that the decays of the b-quark occur via pure right-handed couplings. We show that the existing lower limits on neutrinoless double beta decay imply that any gauge model realizing this idea must have either an $L_e-L_\mu$ or $L_e-L_\tau$ symmetry. We then show that constraints of cosmology together with observations from SN1987A imply that the right-handed neutrinos in this model must be heavier than about 100 MeV in general. In one special case with the $L_e-L_\mu$ symmetry, the $\nu_{\tau_R}$ is heavier than 2 GeV so that this particular version of the model is already ruled out.

We consider possible experimental tests of recent hypotheses suggesting that TeV photons survive the pair production interaction with extragalactic background light over cosmological distances by converting to axion-like particles (ALPs) in galactic magnetic fields. We show that proposed giant ultra-low background scintillation detectors will even have a difficult time reaching the present CAST sensitivity, which is one to two orders of magnitude less sensitive than necessary for a meaningful test of the ALP-photon oscillation hypothesis. Potential alternative tests are briefly discussed., Comment: 4 pages, no figures

Supernova 1987A constraints on the decay mode [Formula: see text] (χ ≡ Majoron) is discussed for the case where the ντ mass is assumed to be 17 keV. Its implications for theoretical models of a 17 keV ντ are considered.

We discuss constraints on electric charge nonconservation and minicharged particles implied by terrestrial, astrophysical and cosmological considerations. We also suggest possible methods for detection of these particles in underground detectors.

Recent measurements of low Q-value beta decay spectra have again suggested the existence of a 17 KeV neutrino. Here we examine a large body of constraints, arising from astrophysics, cosmology, nuclear physics and elementary particle physics, on this particle. By comparing the derived bounds on its lifetime, decay modes and possible electromagnetic properties with a variety of model speculations on its nature, we conclude that such a particle is unlikely. Conversely, if such a neutrino were shown conclusively to exist, it would have profound implications for the nature of the symmetry breaking in the weak leptonic sector. It would most probably imply the existence of physical Goldstone bosons.

Solar-axion interaction rates in NaI, CsI and Xe scintillators via the axio-electric effect were calculated. A table is presented with photoelectric and axioelectric cross sections, solar-axion fluxes, and the interaction rates from 2.0 to 10.0 keV. The results imply that annual-modulation data of large NaI and CsI arrays, and large Xe scintillation chambers, might be made sensitive enough to probe coupling to photons at levels required to explain axion-photon oscillation phenomena proposed to explain the survival of high-energy photons traveling cosmological distances. The DAMAA/LIBRA data are used to demonstrate the power of the model-independent annual modulation due to the seasonal variation in the earth sun distance., 7 pages and no figures

The effects of absorption in the gas, and of density variations on the sensitivity of gas-filled solar-axion helioscopes are theoretically investigated. It is concluded that the 10-meter long CAST helioscope, the most sensitive experiment to date is near the limit of sensitivity in axion mass. Increasing the length, gas density, or tilt angle all have negative influences, and will not improve the sensitivity., 8 pages, 2 figures

We suggest the possibility that in ADD type brane-world scenarios, the higher KK excitations of the graviton may decay to lower ones owing to a breakdown of the conservation of extra dimensional “momenta” and study its implications for astrophysics and cosmology. We give an explicit realization of this idea with a bulk scalar field �, whose nonzero KK modes acquire vacuum expectation values. This scenario helps to avoid constraints on large extra dimensions that come from gamma ray flux bounds in the direction of nearby supernovae as well as those coming from diffuse cosmological gamma ray background. It also relaxes the very stringent limits on reheat temperature of the universe in ADD models.

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., 9 pages, 2 figures Please note that Nussinov has previously submitted entries to the ArXives through assistance of other individuals. The submitter of this paper (robinet@physics.umd.edu) is L. Robinette, administrative assistant to the Maryland TQHN Group; comments should be addressed to nussinov@ccsg.tau.ac.il

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 $\aa$ and $\bar{K}$ and $\aa$ 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., Comment: 5 pages

In this paper we discuss some aspects of the inclusive decays of charmed mesons and also decays of the \ensuremath{\tau} lepton into ${\ensuremath{\nu}}_{\ensuremath{\tau}}+7\ensuremath{\pi}.$ We find that phase space effects are likely to explain the observed lifetime ratio $\ensuremath{\tau}{(D}_{s}^{+})/\ensuremath{\tau}{(D}^{0})=1.17.$ In particular one need not appeal to a large annihilation contribution in the inclusive ${D}^{0}$ decay which, being absent in ${D}_{s}^{+}$ decays, could also contribute to the enhanced ${D}^{0}$ decay rate relative to that of the ${D}_{s}^{+}.$ Examining a separate problem, we find that the rate for $\stackrel{\ensuremath{\rightarrow}}{\ensuremath{\tau}}{\ensuremath{\nu}}_{\ensuremath{\tau}}+7\ensuremath{\pi}$ is almost completely dominated by the tiny phase space for the final eight particle state. Using an effective chiral Lagrangian to estimate the matrix element yields a branching ratio into the channel of interest far smaller than the present upper bound.

We argue that the exactly computable, angle dependent, Casimir force between parallel plates with different directions of conductivity can be measured., Comment: One Figure, 11 pages

LEP data put strong constraints on theoretical speculations about new particles decaying hadronically.

We discuss the cosmological implications as well as possible observability of massive, stable, colored particles which often appear in the discussion of physics beyond the standard model. We argue that if their masses are more than a few hundred GeV and if they saturate the halo density and/or occur with closure density of the universe, they are ruled out by the present WIMP search experiments as well as the searches for anomalous heavy isotopes of ordinary nuclei. We then comment on the possibility that these particles as well as the monopoles could be responsible for the ultra high energy cosmic rays with energy $\geq 10^{20}$ eV and point out that their low inelasticity argues against this., 9 pages; UMD-PP-98-17

Weakly Interacting Massive Particles (WIMPs) may constitute most of the matter in the Universe. There are intriguing results from DAMA/LIBRA, CoGeNT and CRESST-II, and more recently CDMS-Si suggesting a relatively light dark matter candidate of mass 2. At the same time, experiments using heavy nuclear targets such as CDMS-Ge and XENON detectors suggest that there is no DM candidates with MW>15 GeV /c2. We review the existing experiments and the problems associated with light mass WIMP detection. We find that all six experiments considered (DAMA, CoGeNT, CRESST, CDMS-Si, CDMS-Ge, XENON) are consistent if one assumes that the mass of WIMP is lower than expected: 3.4W2. This is followed by a discussion of the properties of "new" detectors, which may enable more reliable detection of low mass WIMPs.

We point out the following astrophysical consequences of a tau neutrino with mass in the MeV range: (i) if it has a small electric charge which will allow it to become a cold dark matter of the universe, then present limits on the 511 KeV gamma ray line rule out the possibility that it contributes an $\Omega_{\nu_{\tau}}$ between .1 to 1 making it unsuitable as a cold dark matter candidate; (ii) if an electrically neutral MeV range $\nu_{\tau}$ decays to $\nu_e + \chi$ ( where $\chi$ is a massless boson) , then its lifetime is bounded by SN1987A observations to be within a window $.05~~sec.\leq \tau(\nu_{\tau})~\leq 300~sec./(m_{\nu_{\tau}}~in~ MeV)$ a range which may be of interest from the point of view of structure formation. Encouraged by the overlap between the range allowed in (ii) above and that required for a proposed structure formation mechanism by Dodelson et al., we search for simple extensions of the standard model, where such masses and lifetimes may arise for natural values of parameters and show that the already existing singlet majoron and low scale left-right models have this property. We also comment on possible familon models for this decay., Comment: UMD-PP-95-21; Latex file, 14 pages

A search was conducted for a light baryon [ital X][sup ++] in the mass range [ital M][sub [ital N]]+[ital M][sub [pi]][ge][ital M][sub [ital X]][ge][ital M][sub [ital N]], by bombarding a CH[sub 2] target with 460 MeV protons, and detecting the products in the Medium Resolution Spectrometer, which was placed at a scattering angle of 15 degrees. No doubly charged baryon in this mass range was detected, thus setting an upper limit of a few tens pb/sr for the reaction. The experiment indicates that if such a light baryon exists its interaction with the ordinary'' physical world is very weak, probably at least 10[sup 7] times weaker than the strong interaction.

Under the assumption that production of the charmed vector meson ${D}^{*}$ is important in the charm threshold region, the soft cascade pion (photon) from ${D}^{*}\ensuremath{\rightarrow}D\ensuremath{\pi}$ (${D}^{*}\ensuremath{\rightarrow}D\ensuremath{\gamma}$) for ${M}_{{D}^{*}}\ensuremath{-}{M}_{D}g{M}_{\ensuremath{\pi}}$ (${M}_{{D}^{*}}\ensuremath{-}{M}_{D}l{M}_{\ensuremath{\pi}}$) could serve as a very useful clue for charmed particles. Also the pions produced in ${e}^{+}{e}^{\ensuremath{-}}$ collisions together with (strong-interaction-stable) charmed particles must obey energy equipartition. This strongly suggests other new heavy-quark thresholds and/or heavy-lepton production.

We analyze further implications of the existence of a massless boson - the Majoron - mainly coupled to left-handed neutrinos. Final lepton spectrum in pion leptonic decay is affected by Majoron bremsstrahlung, yielding a bound on Majoron-neutrino coupling from experimental data. Supernova dynamics is another issue discussed here. We address possible effects of the frequent neutrino-neutrino collisions, neutrino interconversion and light boson bremsstrahlung in neutrino scattering. In particular, we focus on the question of lepton number non-conservation. We find that deleptonization of the core and high-entropy collapse can occur, via a subtle interplay of neutrino interconversion and light boson bremsstrahlung. Then, we propose an unorthodox solution to the missing mass problem in the universe. Finally, we address the problem of galaxy formation, which appears in a new perspective within our model.

Some observations about mass and scattering length inequalities in QCD-like theories are presented. It is shown that the Weingarten mass inequality can be used to argue that global vector symmetries are unbroken in such theories. For QCD, in the limit Nc→ ∞, it is shown that M baryon ⩾ 1 2 N c M meson , provided there are at least Nc degenerate flavors of quarks. It is argued that when there are no bound states in a scattering channel, the mass inequalities can be used to derive inequalities between scattering lengths. Some rigorous inequalities for two and higher point functions for operators bilinear in currents are derived, and used to extract inequalities between quartic coupling constants.

We suggest that mixed heavy quark bound states like\(b\bar c\) may offer very good testing ground for Q.C.D. We make a prediction within ≈0.3% for the\(b\bar c\) ground state mass and discuss its possible production in weak decays.

We discuss several features of the class of planar Feynman diagrams in perturbation theory. We show that the number of planar n -loop diagrams grows exponentially in n in any field theory, and calculate the detailed asymptotic behavior for φ 3 and φ 4 . We discuss the implications of this result for the convergence of the series and its relation to various semiclassical instabilities, with special reference to non-Abelian gauge theories. We also derive a functional integral equation for planar graphs.

We calculate partial widths for the decay of theB-meson into all possible charmonium states and estimate the corresponding branching ratios.

We describe a simple, intuitive picture of how thermal fluctuations in the fields of a system with spontaneously broken symmetry lead to symmetry-restoring phase transitions at finite temperature.

We propose a new test for the triplet majoron model by using neutrino bursts from supernova explosions. These pulses suffer scatterings on the cosmological majoron background. As a consequence, they get spread and their energy spectrum is changed with respect to the conventional expectation. We find that positive evidence of distinct neutrino pulses of all species corresponding to muon and tau-neutrinos heavier than 70 eV would rule out the model.

We estimate the contribution to psi photoproduction from its conventional hadronic components by using an epsilon-exchange model. The results, which are too small, are compared with the parallel rho' case. A reduction factor is observed which also plays an important role in other models. We discuss, in particular, its occurrence in a peripheral model which assumes dominance of new states in the psi fragmentation vertex which interact strongly with conventional hadrons. The strong reduction factor follows from the mismatch between production thresholds and particle masses. Its role is discussed at length and compared with different points of view. (AIP)

It is suggested that monopole-antimonopole pair production initiated by pointlike particles (electrons, quarks) has widely different cross sections in the two cases of ''pointlike'' and composite monopoles, respectively. Production of 't Hooft--Polyakov monopoles is expected to be suppressed by a hugh factor, > or =10/sup 30/. Furthermore, astrophysical evidence is presented suggesting that monopoles with m/sub m/roughly-equal10/sup 4/ GeV/c/sup 2/ cannot be pointlike.

We present some detailed estimates of associated heavy-flavour bound states produced in e+e− annihilations. The calculation is done to lowest order in QCD and we attempt to clarify some ambiguities concerning its range of applicability. The QCD estimates are compared with competing QED (two-photon exchanges) and weak (t decay) channels.

We suggest that the ultimate remnant of an evaporating black hole is an infinitely degenerate particle at the Planck mass. Arguments are presented for the stability of these objects and their cosmological and theoretical implications are briefly discussed.

We argue here that many (up to around 30 species) so far undetected Goldstone bosons could exist in nature, for example, associated with the spontaneous breaking of a horizontal global symmetry, provided the breaking scale is V ≳ 1010 GeV. Since Goldstone bosons do not generate r−1 but spin-dependent r−3 non-relativistic long-range potentials, the apparently most dramatic effect of massless bosons (new long-range forces competing with gravitation and electromagnetism) is easily avoidable (the Glasgow-Weinberg-Salam breaking scale is enough); μ→eG and K→πG provide the most restrictive bounds and probably the only possibility to look for Goldstone bosons in the laboratory.

We propose a model for the psi particles in which these objects are made of unconfined constituents. In our picture no analogs of charmed particles exist, and no Okubo--Zwieg--Iizuka rule is needed. (AIP)

We discuss the possibility of loosely bound states near the charm threshold in the charmed-particle and antiparticle system such as\(D\bar D, D*\bar D*\), etc. An explicit calculation shows that theS- andP-wave states exist in the\(D\bar D\) system with reasonable values for the parameters of the interaction. These bound states may be very close to threshold with large sizes (r.m.s.≳1 fm). Characteristics of these molecularlike states and their relationship with the quark model\(c\bar c\) bound states are also discussed.

We investigate in the framework of the triplet majoron model various additional physical manifestations which should occur if the recent suggestion of Bahcall, Petcov, Toshev and Valle that the electron neutrino decays into the muon neutrino and a majoron en route from the sun is indeed correct. We find no observable manifestation which could rule out this suggestion. Furthermore we show that the parameter chosen to make the decay lifetime of B8 neutrinos comparable with 500 s, the sun-earth transit time, is natural at least in the sense that much (100–1000 times) shorter life times can be ruled out. We observe that only decays ν e → ν μ +X 0 , where the unobservable X0 carries two units of lepton number, avoid prohibitively large (> 99% branching) μ→e+X0 transitions. This selects uniquely the triplet majoron model — or variants thereof — as the theoretical framework for decaying neutrinos.

In essentially all common models of the psi particles off-diagonal couplings such as psi'psi$pi$$pi$ are expected to be greatly suppressed relative to diagonal couplings such as psipsi$pi$$pi$. It is pointed out that this is counter-indicated by the data, leading to important constraints on model building. (AIP)

We discuss the theoretical implications of having the D + lifetime be much greater than that of the D 0 . A consistent phenomenology of D-decay obtains if one assumes sextet dominance and strong color clustering.

It is pointed out that if: (a) at least one technibaryon is very stable (τ ⩾ 10 20−25 yr) and (b) a technibaryon excess is built up at the early stages of the big bang with magnitude comparable to the normal baryonic matter asymmetry ϵ B ≈ ϵ TB then stable technibaryons can account for the missing mass and most naturally explain why ϱ B ≈ 10 −2 ϱ crit .

The survival probability of solar electron neutrinos after non-adiabatic passage through the resonance-oscillation region in the Sun is discussed for the case of three generations. A method to calculate three-generation Landau-Zener transition probabilities between adiabatic states is described. We also discuss how the Landua-Zener probability is modified in the extreme non-adiabatic case.