Search

We discuss a simple non-supersymmetric model based on the electroweak gauge group SU(2)L × SU(2)′ × U(1)B-L where the lightest of the right-handed neutrinos, which are part of the leptonic doublet of SU(2)′, play the role of a long-lived unstable dark matter with mass in the multi-PeV range. We use a resonant s-channel annihilation to obtain the correct thermal relic density and relax the unitarity bound on dark matter mass. In this model, there exists a 3-body dark matter decay mode producing tau leptons and neutrinos, which could be the source for the PeV cascade events observed in the IceCube experiment. The model can be tested with more precise flavor information of the highest-energy neutrino events in future data., SCOPUS: ar.j, info:eu-repo/semantics/published

Strange quark matter made of up, down and strange quarks has been postulated by Witten [E. Witten, Phys. Rev D 30 (1984) 279]. Strange quark matter would be nearly charge neutral and would have density of nuclear matter (1014 gm/cm3). Witten also suggested that nuggets of strange quark matter, or strange quark nuggets (SQNs), could have formed shortly after the Big Bang, and that they would be viable candidates for cold dark matter. As suggested by de Rujula and Glashow [A. de Rujula and S. Glashow, Nature 312 (1984) 734], an SQN may pass through a celestial body releasing detectable seismic energy along a straight line. The Moon, being much quieter seismically than the Earth, would be a favorable place to search for such events. We review previous searches for SQNs to illustrate the parameter space explored by using the Moon as a low-noise detector of SQNs. We also discuss possible detection schemes using a single seismometer, and using an International Lunar Seismic Network.

It was pointed out in 1984 by Witten that strange quark matter (SQM) – matter made of up, down, and strange quarks (rather than just up and down, as are protons and neutrons) – might well be stable and the lowest energy state of matter. The reason is that it would be electrically neutral and have less Pauli-Principle repulsion. Binding would increase with numbers of quarks, and might not begin below thousands. It would have nuclear density. Neutron stars would be strange quark stars; and it might conceivably constitute dark matter. One way to detect ton-range SQM nuggets (SQNs) would be from seismic signals they would make passing through the Earth. We give a rough estimate on the relative advantage of attempting to detect SQNs on the Moon over Earth (about 50 times more detections).

(1) Quark nugget . Twenty years ago, Witten pointed out that matter made of up, down and strange quarks is (by the Pauli Principle) more likely to be stable than matter made of just up and down. If stable, it could exist in macroscopic nuggets of nuclear densities. We searched about a million seismic reports to the US Geological Survey (1990–1993) for evidence of such (multi-ton) nuggets passing through the Earth. We found one set of 9 reports with first signal timing and directions and subsequent wave forms all consistent with nugget passage, but not consistent with point events such as Earthquakes, nor with statistics of random reports. Others, however, showed that our results were incorrect because of a problem with the clock of one reporting station. (2) Quinton radiation . If the accelerating expansion of the universe is due to a quintessence field, radiation of quintessence quanta (or “quintons” I like to call them) could be an energy loss mechanism for binary systems. We calculated its strength assuming only the minimal interaction required by general covariance. We considered both the case in which the zero order field varies only over cosmic times and distances and that in which it is modified my nearby masses. For the former, the effect is too small to be observable. For the latter , we bound a parameter in the quintessence field solution in the presence of a large mass by requiring that the effect be small for the Hulse–Taylor pulsar.

In 1984 Edward Witten proposed that an extremely dense form of matter composed of up, down, and strange quarks may be stable at zero pressure (Witten, 1984). Massive nuggets of such dense matter, if they exist, may pass through the Earth and be detectable by the seismic signals they generate (de Rujula and Glashow, 1984). With this motivation we investigated over 1 million seismic data reports to the U.S. Geological Survey for the years 1990-1993 not associated with epicentral sources. We report two results: (1) with an average of about 0.16 unassociated reports per minute after data cuts, we found a significant excess over statistical expectation for sets with ten or more reports in ten minutes; and (2) in spite of a very small a priori probability from random reports, we found one set of reports with arrival times and other features appropriate to signals from an epilinear source. This event has the properties predicted for the passage of a nugget of strange quark matter (SQM) through the earth, although there is no direct confirmation from other phenomenologies., Comment: 23 pages, 9 figures, one previously described event eliminated, extensive examination of the second event as a possible association of random reports, additional analysis of the data set, search algorithms, and waveforms

Strongly interacting neutral massive particles (SIMPs) have been proposed as candidates for dark matter, as the lightest supersymmetric particle, as a possible explanation for ultra-high-energy cosmic rays, and as a dark matter solution to galactic structure problems. If bound to nuclei, SIMPs could manifest themselves as anomalously heavy isotopes of known elements. We analyze the results from a recent experimental search for SIMPs in a collection of gold and iron samples with various exposures to cosmic rays and to a SIMP component of dark matter. The samples included gold flown on the NASA Long-Duration Exposure Facility, as well as geological samples and an iron meteorite. We show that the bounds on SIMPs from that experiment can be used to set nontrivial constraints on the SIMP contribution to the cosmological density parameter Ω.

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

We compute the temperature and IR signal of particles of radius $a$ and albedo $\alpha$ at heliocentric distance $R$, taking into account the emissivity effect, and give an interpolating formula for the result. We compare with analyses of COBE DIRBE data by others (including recent detection of the cosmic IR background) for various values of heliocentric distance, $R$, particle radius, $a$, and particle albedo, $\alpha$. We then apply these results to a recently-developed picture of the Kuiper belt as a two-sector disk with a nearby, low-density sector (40

We review the romance and mystery of strange quark matter (SQM), including: its basics, our recent work on bounds on the abundance of ton-range strange quark nuggets (SQNs) from Earth seismology, potential SQN bounds from a possible seismic search on the Moon, and our recent bounds on SQNs in the 10 kilogram to ton range from the data of Apollo-implanted seismometers. Finally, we speculate a bit on using the sun or the solar system to detect passage of SQNs of much greater mass than the aforementioned.

We find constraints on heavy, stable, strongly interacting massive particles (X) from searches for anomalous nuclei containing them, formed during primordial nucleosynthesis. Using existing data, we obtain a limit on the abundance ratio $C_X\equiv n_X/n_B$ in the range of $3\times 10^{-8}$ to $3\times 10^{-13}$ for masses up to 10 TeV if the $X-N$ interaction is sufficiently strong to bind in low Z nuclei. We also find a rough lower limit on the $X-N$ interaction that implies binding in nuclei with $A\geq 200$ over much of the $M_X$ range of interest, and address the relative abundance of such anomalous nuclei on Earth., Comment: 11 pages; Final version; to appear in Phys. Rev. Letters

One of the most important questions in the study of compact objects is the nature of pulsars, including whether they consist of neutron matter or strange quark matter (SQM). However, few mechanisms for distinguishing between these two possibilities have been proposed. The purpose of this paper is to show that a strange star (one made of SQM) will have a vibratory mode with an oscillation frequency of approximately 250 GHz (millimeter wave). This mode corresponds to motion of the center of the expected crust of normal matter relative to the center of the strange quark core, without distortion of either. Radiation from currents generated in the crust at the mode frequency would be a SQM signature. We also consider effects of stellar rotation, estimate power emission and signal-to-noise ratio, and discuss briefly possible mechanisms for exciting the mode., 13 pages, Latex, one figure

We extract information from the failure of small objects to cause detectable damage to Pioneer 10, which has been inside the Kuiper Belt for a decade. Belt objects too small for telescope detection and too large for IR emission visibility are addressed. This is a size range with few other potential techniques, short of a new space mission, for direct detection. Results, based on an 8-inch radius propellant tank, are bounds of about 1/10th of an Earth mass on low-mass, low-density objects. Implications of Poynting–Robertson drag and ISM erosion, and potential improvements to the bounds, are discussed.

We consider the implications of fermionic asymmetric dark matter for a "mixed neutron star" composed of ordinary baryons and dark fermions. We find examples, where for a certain range of dark fermion mass -- when it is less than that of ordinary baryons -- such systems can reach higher masses than the maximal values allowed for ordinary ("pure") neutron stars. This is shown both within a simplified, heuristic Newtonian analytic framework with non-interacting particles and via a general relativistic numerical calculation, under certain assumptions for the dark matter equation of state. Our work applies to various dark fermion models such as mirror matter models and to other models where the dark fermions have self interactions., 20 pages, 6 figures

Since Witten's seminal 1984 paper on the subject, searches for evidence of strange quark nuggets (SQNs) have proven unsuccessful. In the absence of experimental evidence ruling out SQNs, the validity of theories introducing mechanisms that increase their stability should continue to be tested. To stimulate electromagnetic SQN searches, particularly space searches, we estimate the net charge that would develop on an SQN in space exposed to various radiation baths (and showers) capable of liberating their less strongly bound electrons, taking into account recombination with ambient electrons. We consider, in particular, the cosmic background radiation, radiation from the sun, and diffuse galactic and extragalactic $\gamma $-ray backgrounds. A possible dramatic signal of SQNs in explosive astrophysical events is noted., Comment: CitationS added, new subsection added, more discussion, same numerical results

Evidence for the Kuiper Belt (of cometary material just past Neptune) and the processes that shape it are briefly reviewed. A summary of selected estimates of its mass is given. A two-sector model for the belt is summarized. A limit is placed on the amount of mass that could be present in the Kuiper Belt in the form of objects with sizes around a centimeter, from survival of the Pioneer 10 spacecraft’s propellant tank during a dozen years in the belt. Work in progress on the belt’s IR signal is reviewed: A useful formula is given for the IR signal from dust particles as a function of albedo, radius and heliocentric distance. Preliminary results are given for limits on the sector masses, in the two-sector model, as a function of time since last passage of the Sun through a giant molecular cloud. Possible indication for the time since such passage and possible support for the existence of a more massive outer sector are found in preliminary results for the ratios of the IR signal in the four different COBE DIRBE bands.

Bounds on masses and abundances of Strange Quark Nuggets (SQNs) are inferred from a seismic search on Earth. Potential SQN bounds from a possible seismic search on the Moon are reviewed and compared with Earth capabilities. Bounds are derived from the data taken by seismometers implanted on the Moon by the Apollo astronauts. We show that the Apollo data implies that the abundance of SQNs in the region of 10 kg to one ton must be at least an order of magnitude less than would saturate the dark matter in the solar neighborhood., Comment: 7 pages and 4 tables, plus 3 attached figures. Revised version responds to helpful comments of Phys. Rev. referee by adding 3 figures, subtracting two tables and taking into account information from QCD

For the Table we see that there is SIMP binding in gold for M S 2 σsn > 5mbGeV 2, and that AMS experiments sensitive to one part in 1020 can detect the existence of SIMPs of mass less than a TeV, while the region of interest for explaining UHECRs can be explored with a sensitivity of one part in 1016 or less. Looking for SIMPs at the Tevatron is more difficult, but over half the region of interest for explaining UHECRs could be searched in the upcoming Run II by looking for (wide) back to back jets with no signal in the central tracker or EM calorimeter. Interested people are urged to send any gold in their possession for which they can prove 107 (or more) years of exposure to Purdue. Almost all nuclei will be returned intact

We show that spontaneous breaking of global $B-L$ symmetry responsible for small neutrino masses via the seesaw mechanism provides a unified picture of hybrid inflation and dark matter if the scale of $B-L$ breaking is close to the GUT scale. The majoron which acquires a small mass in the milli-eV range due to Planck scale breaking of $B-L$ is the dark matter candidate. The coupling of the majoron field to the neutrino induces a small violation of CPT and Lorentz invariance at the present epoch. We discuss some of the phenomenological and cosmological implications of the model., 15 pages, 4 figures

Recent astrophysical observations have provided strong evidence that the present expansion of the universe is accelerating, powered by the energy density associated with a cosmological term. Assuming the latter to be not simply a constant term but a "quintessence" field, we study the radiation of quanta of such a "quintessence" field ("quintons") by binary systems of different types and compare intensities to those of standard tensor gravitational wave emission. We consider both the case in which the quintessence field varies only over cosmological distances and the case in which it is modified spatially by (strong) gravitational fields, a condition that results in bounds on the gradient of the scalar field. We show that, in both the first case and, because of a bound we derive from the Hulse-Taylor pulsar, in the second, there is not sufficient quinton radiation to affect expected LISA and LIGO gravity wave signals from binary systems. We show that, in the second case, the Large Hadron Collider is capable of setting a bound similar to that from the binary pulsar., 12 pages aastex, accepted for publication in the Astrophysical Journal. Minor typographical errors and reference list corrected

There are a number of theoretical motivations for searching for anomalously heavy isotopes ${}_{Z}X$ of known elements, where Z is the nuclear charge of the anomalous nucleus X. Such nuclei could arise from the binding of a new strongly interacting massive particle (SIMP) to the nucleus of a known element, and could thus be detected as an anomalously heavy isotope of that element. SIMPs have been proposed as candidates for dark matter, and for the lightest supersymmetric particle, as well as a possible explanation for ultra high-energy cosmic rays. A search for anomalous nuclei X has been performed by analyzing several unique samples including gold nuggets collected in Australia, Arizona and North Carolina, gold foils flown on NASA's LDEF satellite, and an Fe meteorite. In each gold sample we scanned for Au isotopes with masses up to $1.67 \mathrm{TeV}{/c}^{2}$ using PRIME Lab, the Purdue accelerator mass spectrometer facility. We have also searched for anomalous Fe isotopes with masses up to $0.65 \mathrm{TeV}{/c}^{2}$ in the iron meteorite sample. We find no evidence for SIMPs in any of our samples, and our results set stringent limits on the abundance of anomalous isotopes of ordinary matter as a function of X mass.

We report the results from an experimental search for strongly interacting massive particles bound to gold nuclei. A scan for heavy gold isotopes with masses ranging from 186.3 to $325.9 \mathrm{GeV}{/c}^{2}$ was performed on laboratory gold and gold from western Australia using PRIME Lab, the Purdue Accelerator Mass Spectrometer facility. The results provide significant new constraints on current models which predict the existence of such particles with abundance ratios in the range ${10}^{\ensuremath{-}11}\char21{}{10}^{\ensuremath{-}10}.$

It has been argued that the observed core density profile of galaxies is inconsistent with having a dark matter particle that is collisionless and alternative dark matter candidates which are self interacting may explain observations better. One new class of self interacting dark matter that has been proposed in the context mirror universe models of particle physics is the mirror hydrogen atom whose stability is guaranteed by the conservation of mirror baryon number. We show that the effective transport cross section for mirror hydrogen atoms, has the right order of magnitude for solving the ``cuspy'' halo problem. Furthermore, the suppression of dissipation effects for mirror atoms due to higher mirror mass scale prevents the mirror halo matter from collapsing into a disk strengthening the argument for mirror matter as galactic dark matter., Comment: 6 pages; some references added

We present a particle physics realization of a recent suggestion by Spergel and Steinhardt that collisional but dissipationless dark matter may resolve the core density problem in dark-matter-dominated galaxies such as the dwarf galaxies. The realization is the asymmetric mirror universe model introduced to explain the neutrino puzzles and the microlensing anomaly. The mirror baryons are the dark matter particles with the desired properties. The time scales are right for the resolution of the core density problem and the formation of mirror stars (MACHOs observed in microlensing experiments). The mass of the region homogenized by Silk damping is between a dwarf and a large galaxy. (c) 2000 The American Physical Society.

Recently, Barger {\em et al.} computed energy losses into Kaluza Klein modes from astrophysical plasmas in the approximation of zero density for the plasmas. We extend their work by considering the effects of finite density for two plasmon processes. Our results show that, for fixed temperature, the energy loss rate per cm$^3$ is constant up to some critical density and then falls exponentially. This is true for transverse and longitudinal plasmons in both the direct and crossed channels over a wide range of temperature and density. A difficulty in deriving the appropriate covariant interaction energy at finite density and temperature is addressed. We find that, for the cases considered by Barger {\em et al.}, the zero density approximation and the neglect of other plasmon processes is justified to better than an order of magnitude., 17 pages, LaTeX2e, 4 figures, 11 tables

We propose that the massive compact halo objects (MACHOs) observed in the recent microlensing experiments with an apparent best fit mass of about $0.5 M_{\odot}$ are objects made out of ``mirror'' baryonic matter rather than familiar baryons. Such a possibility arises naturally within the framework of mirror matter models proposed recently to accomodate the sterile neutrinos that seem necessary to solve all the neutrino puzzles simultaneusly. We show that for mirror matter parameters that fit the neutrino observations, the maximum mass of mirror stars are of order $0.5 M_{\odot}$ and their main sequence lifetime is much less than the age of the universe. They are therefore likely to be black holes. Mirror matter machos have the advantage that they do not suffer from the problems encountered in the conventional red, brown or white dwarf interpretation. The calculations also apply to the question of how the world of familiar matter would be different if all fundamental mass parameters were., Comment: 9 pages, 3 figures

We consider nuclei produced in core collapse supernovae and subjected to a high neutron flux. We show that an accelerator mass spectrometry experiment that searched for traces of anomalous iron isotopes could set limits on the order of $10^{-20}-10^{-25}$ on (or perhaps discover) Pauli principle violation by neutrons. A similar search for anomalous Co isotopes could set limits in the range $10^{-13}-10^{-18}$ on Pauli principle violation by protons. We show that existing data on Oxygen can be used to set a limit of about $10^{-17}$ in one proposed model of such violation., Comment: 11 pages; UMD-PP-99-014

In supergravity models with low supersymmetry breaking scale the gravitinos can be superlight, with mass in the 10{sup -6} eV to few keV range. In such a case, gravitino emission provides a new cooling mechanism for protoneutron stars and therefore can provide constraints on the mass of a superlight gravitino. This happens because the coupling to matter of superlight gravitinos is dominated by its goldstino component, whose coupling to matter of superlight gravitinos is dominated by its goldstino component, whose coupling to matter is inversely proportional to the scale of supersymmetry breaking and increases as the gravitino mass decreases. Present observations therefore provide lower limits on the gravitino mass. Using the recently revised goldstino couplings, we find that the two dominant processes in supernova cooling are e{sup +} e{sup -} {yields} GG and {gamma}+e{sup -} {yields} e{sup -} GG. They lead to a lower limit on the supersymmetry breaking scale {Lambda}{sub s} from 160 to 500 GeV for core temperatures 30 to 60 MeV and electron chemical potentials 200 to 300 MeV. The corresponding lower limits on the gravitino mass are .6 - 6 x 10{sup -6} eV.

We briefly review the status of strange quark matter and the capabilities of seismic networks for detecting nuggets of strange quark matter that pass through the Earth if an appreciable fraction of galactic halo dark matter is in the form of ton-sized nuggets. We describe progress to date in analyzing 13 years of seismic data and we note the possibility that new networks under development for verifying compliance with the recently negotiated Comprehensive Test Ban Treaty might be capable of contributing to detection of such nuggets.

The idea of the universe with a mirror sector having all particles and forces identical to those in the familiar sector has been proposed in the context of neutrino physics as well as superstring theories. Assuming that all the quark and charged lepton masses in the mirror universe are scaled by a common factor, $\zeta$, as is required in one interpretation of the neutrino data, we investigate domains of the parameter $\zeta$ where physical conditions are favorable for cooling in the age of the universe that can lead to the formation of compact structures given the initial condition $\Omega_B =\Omega_{\tilde{B}}$ ($\tilde{B}$ denoting the mirror baryon). In particular we ask whether there is a region in $\zeta$-space for which primordial Jeans mass mirror clouds cannot cool in the present age of the universe. We find that for most of the area of interest in the parameter space, atomic hyperfine structure cooling is effective in a time period short compared to the age of the universe but long compared to the free fall time for globular-sized objects expected on the basis of simple Jeans length analysis., Comment: 21 pages, Latex file and one postscript file of figure appended

We consider the possibility that a light sterile-neutrino species $\nu_S$ can be produced by $\nu_e$ scattering during the cooling of a proto-neutron star. If we parameterize the sterile neutrino production cross-section by a parameter $A$ as $\sigma (\nu_e X\rightarrow \nu_S X) = A \sigma(\nu_e X\rightarrow \nu_e X)$, where $X$ is an electron, neutron or proton, we show that $A$ is constrained by limits to the conversion of $\nu_e$ to $\nu_S$ in the region between the sterile-neutrino trapping region and the electron-neutrino trapping region. This consideration excludes values of $A$ in the range between $10^{-4} \la A \la 10^{-1}$., Comment: 12 pages; Latex

We improve, using a larger set of observations including Voyager 2 Neptune flyby data, previous bounds on the amount of dark matter (DM) trapped in a spherically symmetric distribution about the sun. We bound DM by noting that such a distribution would increase the effective mass of the sun as seen by the outer planets and by finding the uncertainty in that effective mass for Uranus and Neptune in fits to the JPL Developmental Ephermeris residuals, including optical data and those two planets' Voyager 2 flybys. We extend our previous procedure by fitting more parameters of the developmental ephemerides. Additionally, we present here the values for Pioneer 10 and 11 and Voyager 1 and 2 Jupiter ranging normal points (and incorporate these data as well). Our principal result is to limit DM in spherically symmetric distributions in orbit about the sun interior to Neptune's orbit to less than an earth mass and interior to Uranus' orbit to about 1/6 of an earth's mass., 23 pages, Latex

We consider the two coupled channels [ital V][sub [ital L]][ital V][sub [ital L]] and [ital HH] where [ital H] is the Higgs boson and [ital V][sub [ital L]] the longitudinal vector boson. We unitarize the tree diagram amplitudes using the coupled channel [ital N]/[ital D] method and compute [ital s]- and [ital p]-wave scattering amplitudes for a range of Higgs boson mass values. We also find values for the Higgs boson mass at which the potential is sufficiently strong to give a bound state below the [ital VV] threshold (around 1.2 TeV for one choice of potential term).

The Higgs boson is a hypothesised particle which, if it exists, would give the mechanism by which particles acquire mass.

Using the grand unified theories, the authors extrapolate cosmic events into a future that is up to 10/sup 100/ times the current age of the universe. The framework for the calculations about the remote future is the big-bang model. From the standpoint of cosmology the importance of the extrapolations is that the grand unified theories have consequences that can be tested in terrestial laboratories, and so the predictions they make under extreme conditions can be confirmed. Since it is not know if the universe is closed or open, the authors give a future for each type universe. The main events for an open universe are: (1) stars will run out of fuel; (2) stars will lose their planets; (3) galactic evaporation; (4) proton decay; (5) decay of black holes. For a closed universe the expansion phase follows the same events as that of the open universe. It is possible that if the universe is closed, it could be cyclic. (SC)

We consider the contribution to stellar energy loss that would result from the existence of a recently proposed very-low-mass (\ensuremath{\lesssim}1 eV) axion. We calculate the energy loss rate of hydrogen-burning stars and of red giants from very-light-axion production through the Primakoff process. The result is an upper bound of about ${10}^{\ensuremath{-}2}$ eV on the mass of such a particle. We also consider briefly the cosmic background produced by the decay products of primordial axions, and the possibility of laboratory measurements of the long-range force a low-mass pseudoscalar boson would create.

We study the reactions ..pi..N..--> pi pi..N in the center-of-mass energy range 1320--1930 MeV within the framework of the isobar model. The present analysis includes over 30% more events than the most extensive previous analysis. Data for ..pi../sup -/p..--> pi../sup +/..pi../sup -/n, ..pi../sup -/p..--> pi../sup 0/..pi../sup -/p, ..pi../sup +/p..--> pi../sup 0/..pi../sup +/p, and ..pi../sup +/p..--> pi../sup +/..pi../sup +/n are simultaneously fitted assuming production of epsilon, rho, ..delta..(P/sub 33/) and N/sup /(P/sub 11/). The cross section for ..pi../sup -/p..--> pi../sup 0/..pi../sup 0/n is predicted and found to be in good agreement with experiment. ..pi..N..--> pi..N( amplitudes for I = (1/2) are investigated for the first time. We confirm the existence of a significant ..pi..N decay for the second P/sub 33/ resonance and determine that ..pi..N( is the dominant inelastic channel for the P/sub 31/ partial wave. The rhoN decay of the G/sub 17/ wave is observed for the first time. Evidence is found for unestablished resonances near 1900 MeV in the S/sub 11/, P/sub 11/, P/sub 13/, and F/sub 15/ partial waves. We also discuss evidence for a second F/sub 35/ resonance. Signs of resonant amplitudes determined from this analysis are compared with results of previous analyses and with predictions frommore » several models.« less

We consider the properties of a relativistic Fermi gas. In particular we derive expressions for the flow velocities behind strong and weak shock waves. We use these results to consider the validity of attempts to bound neutrino-neutrino cross sections from the supernova SN1987A. Certain apporaches to such bounds appear to be invalid. We also apply this picture to a recently proposed scenario for galaxy formation in the presence of light neutrinos with large cross sections.

Lower bounds on the mass of a light scalar (Higgs) or pseudoscalar (axion) particle are found in three ways: (1) by requiring that their effect on primordial nucleosynthesis not yield a deuterium abundance outside present experimental limits, (2) by requiring that the photons from their decay thermalize and not distort the microwave background, and (3) by requiring that their emission from helium-burning stars (red giants) not disrupt stellar evolution. The best bound is from (3); it requires the axion or Higgs-particle mass to be greater than about 0.2 MeV.

An isobar-model partial-wave analysis of 4140 ${\ensuremath{\pi}}^{\ensuremath{-}}p\ensuremath{\rightarrow}{\ensuremath{\pi}}^{+}{\ensuremath{\pi}}^{\ensuremath{-}}n$ bubble-chamber events at total center-of-mass energies between 1330 and 1380 MeV is reported. Included in the analysis is a chiral-symmetry background calculated from the phenomenological Lagrangian. Significant results of the analysis are that production is dominated by the initial $P11$ wave and that, in this wave, final-state $\ensuremath{\epsilon}N$ production is more important than $\ensuremath{\pi}\ensuremath{\Delta}$ production. We show that the recent single-arm-spectrometer data confirm the bubble-chamber data, where the two overlap. We discuss the determination of the chiral-symmetry-breaking parameter $\ensuremath{\xi}$. The analysis establishes that the present data is consistent with several models of the symmetry breaking, although it favors the vector breaking model of Weinberg, $\ensuremath{\xi}=0$. Using a dispersion relation we show that $\ensuremath{\epsilon}N$ production in the tail of the Roper ($P11$) resonance significantly affects the extraction of $\ensuremath{\xi}$ from total-cross-section data; hence in pion production $\ensuremath{\xi}$ cannot be determined independently of the isobar amplitudes. As a further application of the results of the analysis we determine the value of the $\ensuremath{\Delta}\ensuremath{\pi}\ensuremath{\Delta}$ coupling constant. Our result depends on the value taken for the $\ensuremath{\Delta}$ mass and what assumptions one makes to determine the large $\ensuremath{\pi}\ensuremath{\Delta}$ amplitudes; but, in any case, it is considerably less than the theoretical predictions which follow from SU(6), U(12), the quark model, and superconvergence relations. We also perform, in this paper, a Goldberger-Treiman-MIT-bag-model calculation which agrees with the other theoretical predictions. We further show that by attributing all $P33$ inelasticity to $\ensuremath{\pi}\ensuremath{\Delta}$ production the results of a recent elastic-phase-shift analysis imply upper bounds on the $\ensuremath{\Delta}\ensuremath{\pi}\ensuremath{\Delta}$ coupling constant which are consistent with the value implied by the isobar analysis.

We calculate the changes in the yields of primordial nucleosynthesis which result from small corrections to rates for weak processes that connect neutrons and protons. We correct the weak rates by improved treatment of Coulomb and radiative corrections, and by inclusion of plasma effects. Our calculations lead to a systematic decrease in the predicted $^{4}\mathrm{He}$ abundance of about $\ensuremath{\Delta}Y=0.0025$. The relative changes in other primordial abundances are also 1-2%.

An upper bound on the lifetime of a massive, neutral, weakly interacting lepton, ${\ensuremath{\nu}}_{H}$, is derived from standard big-bang cosmology. Saturation of the bound and reasonable assumptions about the weak interaction of the ${\ensuremath{\nu}}_{H}$ then yield a prediction of approximately 10 MeV for its mass.

If there exist neutral leptons with masses in the range 50 eV to 5 GeV, they would have been present in thermal equilibrium in the early stages of the hot big bang. In the subsequent evolution of the universe, if their lifetime is sufficiently long, their mass dominated the energy density of the universe. The effect of their presence on the synthesis of elements in the early universe is considered. Of the observed primordial abundances, the helium abundance was found to be independent of their existence, but the deuterium abundance was found to be sufficiently sensitive to allow bounds to be placed on the mass, lifetime, and decay modes of any heavy neutrinos. In particular, on the basis of present best estimates of astrophysical parameters, previous radiative lifetime bounds on the order of months are reduced to bounds on the order of hours, and expand the range of masses for which no radiatively decaying massive neutral leptons are allowed, to 50 to 100 keV.

We calculate the abundances of anomalous light, Z>1 nuclei that would be produced by primordial nucleosynthesis if there exist new neutral, stable baryons.

The electromagnetic mass differences of the pseudoscalar and vector mesons are calculated in the bag model. The electromagnetic mass difference of the charmed pseudoscalar (D) is predicted to be 7.82 MeV; and that of the D*, 6.81 MeV. (AIP)