arXiv subjects

F. Halzen

Publications and source records attributed to F. Halzen.

At least 127 records · Page 7Linked to original sources

arXiv1996

The Case for a Kilometer-Scale High-Energy Neutrino Detector: 1996

The objective of neutrino astronomy, born with the identification of thermonuclear fusion in the sun and the particle processes controlling the fate of a nearby supernova, is to build instruments which reach throughout and far beyond our Galaxy and make measurements relevant to cosmology, astrophysics, cosmic-ray and particle physics. These telescopes will push astronomy to wavelengths smaller than $10^{-14}$~cm by mapping the sky in high-energy neutrinos instead of high-energy photons to which the Universe is partially opaque. While a variety of collaborations are pioneering complementary methods by building neutrino detectors with effective area in excess of 0.01~km$^2$, we show here that the science dictates 1~km$^2$, or a 1~km$^3$ instrumented volume, as the natural scale of a high-energy neutrino telescope. The construction of a high-energy neutrino telescope therefore requires a huge volume of very transparent, deeply buried material such as ocean water or ice, which acts as the medium for detecting the particles. We will speculate on its architecture. The field is immersed in technology in the domain of particle physics to which many of its research goals are intellectually connected. With several thousand optical modules the scope of constructing a kilometer-scale instrument is similar to that of experiments presently being commissioned such as the SNO neutrino observatory in Canada and the Superkamiokande experiment in Japan.

astro-ph↗

arXiv1996

Composition of Primary Cosmic Rays Beyond the ``Knee''from Emulsion Chamber Observations

We show that the simplest assumptions for the dynamics of particle production allow us to understand the fluxes of hadrons and photons at mountain altitudes as well as the structure of individual events. The analysis requires a heavy nuclear component of primary cosmic rays above the ``knee" in the spectrum with average mass number $ = 7.3 \pm 0.9$.

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arXiv1996

Neutrinos from Gamma Ray Bursts

We show that the detection of neutrinos from a typical gamma ray burst requires a kilometer-scale detector. We argue that large bursts should be visible with the neutrino telescopes under construction. We emphasize the 3 techniques by which neutrino telescopes can perform this search: by triggering on i) bursts of muons from muon neutrinos, ii) muons from air cascades initiated by high energy gamma rays and iii) showers made by relatively low energy ($\simeq 100\,\mev$) electron neutrinos. Timing of neutrino-photon coincidences may yield a measurement of the neutrino mass to order $10^{-5}$~eV, an interesting range in light of the solar neutrino anomaly.

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arXiv1995

Ultra-Transparent Antarctic Ice as a Supernova Detector

We have simulated the response of a high energy neutrino telescope in deep Antarctic ice to the stream of low energy neutrinos produced by a supernova. The passage of a large flux of MeV-energy neutrinos during a period of seconds will be detected as an excess of single counting rates in all individual optical modules. We update here a previous estimate of the performance of such an instrument taking into account the recent discovery of absorption lengths of several hundred meters for near-UV photons in natural deep ice. The existing AMANDA detector can, even by the most conservative estimates, act as a galactic supernova watch.

astro-ph↗

arXiv1995

The Search for Neutrino Sources Beyond the Sun

The hope is that in the near future neutrino astronomy, born with the identification of thermonuclear fusion in the sun and the particle processes controlling the fate of a nearby supernova, will reach throughout and beyond our Galaxy and make measurements relevant to cosmology, astrophysics, cosmic-ray and particle physics. The construction of a high-energy neutrino telescope requires a huge volume of very transparent, deeply buried material such as ocean water or ice, which acts as the medium for detecting the particles. The AMANDA muon and neutrino telescope, now operating 4 strings of photomultiplier tubes buried in deep ice at the South Pole, is scheduled to be expanded to a 10-string array. The data collected over the first 2 years cover the 3 basic modes in which such instruments are operated: i) the burst mode which monitors the sky for supernovae, ii) the detection of electromagnetic showers initiated by PeV-energy cosmic electron neutrinos, and iii) muon trajectory reconstruction for neutrino and gamma-ray astronomy. We speculate on the possible architectures of kilometer-scale instruments, using early data as a guideline.

astro-ph↗

arXiv1995

Colorless States in Perturbative QCD: Charmonium and Rapidity Gaps

We point out that an unorthodox way to describe the production of rapidity gaps in deep inelastic scattering, recently proposed by Buchmüller and Hebecker, suggests a description of the production of heavy quark bound states which is in agreement with data. The approach questions the conventional treatment of the color quantum number in perturbative QCD.

hep-ph↗

arXiv1995

The Direct and Indirect Detection of Weakly Interacting Dark Matter Particles

An ever-increasing body of evidence suggests that weakly interacting massive particles (WIMPs) constitute the bulk of the matter in the Universe. We illustrate how experimental data, dimensional analysis and Standard Model particle physics are sufficient to evaluate and compare the potential of detectors searching for such particles either directly (e.g.\ by their scattering in germanium detectors), or indirectly (e.g.\ by observing their annihilation into neutrinos in underground detectors).

astro-ph↗

arXiv1995

Gamma Ray Astronomy with Underground Detectors

Underground detectors measure the directions of up-coming muons of neutrino origin. They can also observe down-going muons made by gamma rays in the Earth's atmosphere. Although gamma ray showers are muon-poor, they produce a sufficient number of muons to detect the sources observed by GeV and TeV telescopes. With a threshold higher by one hundred and a probability of muon production of about $1\%$ for the shallower AMANDA and Lake Baikal detectors, these instruments can, for a typical GRO source, match the detection efficiency of a GeV satellite detector since their effective area is larger by a factor $10^4$. The muons must have enough energy for accurate reconstruction of their direction. Very energetic muons on the other hand are rare because they are only produced by higher energy gamma rays whose flux is suppressed by the decreasing flux at the source and by absorption on interstellar light. We show that there is a window of opportunity for muon astronomy in the 100~GeV energy region which nicely matches the threshold energies of the AMANDA and Lake Baikal detectors.

hep-ph↗

arXiv1995

The Direct and Indirect Detection of Weakly Interacting Dark Matter Particles

An ever-increasing body of evidence suggests that weakly interacting massive particles (WIMPs) constitute the bulk of the matter in the Universe. Experimental data, dimensional analysis and Standard Model particle physics are sufficient to evaluate and compare the performance of detectors searching for such particles either directly (e.g.\ by their scattering in germanium detectors), or indirectly (e.g.\ by observing their annihilation into neutrinos in underground detectors). We conclude that the direct method is superior if the WIMP interacts coherently and its mass is lower or comparable to the weak boson mass. In all other cases, i.e.\ for relatively heavy WIMPs and for WIMPs interacting incoherently, the indirect method will be competitive or superior, but it is, of course, held hostage to the successful deployment of high energy neutrino telescopes with effective area in the $\sim10^4$--$10^5$~m$^2$ range and with appropriately low threshold. The rule of thumb is that a kilogram of germanium is roughly equivalent to a $10^4$~m$^2$ neutrino telescope, although the signal-to-noise is, at least theoretically, superior for the neutrino detector. The energy resolution of the neutrino telescope may be exploited to measure the WIMP mass and suppress the background. A kilometer-size detector probes WIMP masses up to the TeV-range, beyond which they are excluded by cosmological considerations.

hep-ph↗

arXiv1995

Particle Production in Very High-Energy Cosmic-Ray Emulsion Chamber Events: Usual and Unusual Events

We show that a simple scaling model of very forward particle production, consistent with accelerator and air shower data, can describe all features of the very high-energy interactions recorded with emulsion chambers. This is somewhat surprising after numerous claims that the same data implied large scaling violations or new dynamics. Interestingly, we cannot describe some of the Centauro events, suggesting that these events are anomalous independently of their well-advertised unusual features such as the absence of neutral secondaries.

hep-ph↗

arXiv1995

SIGNATURES OF CP-VIOLATION IN THE PRESENCE OF MULTIPLE B-PAIR PRODUCTION AT HADRON COLLIDER

We calculate the production of 2 b-quark pairs in hadron collisions. Sources of multiple pairs are multiple interactions and higher order perturbative QCD mechanisms. We subsequently investigate the competing effects of multiple b-pair production on measurements of CP-violation: i) the increase in event rate with multiple b-pair cross sections which may reach values of order 1 barn in the presence of multiple interactions and ii) the dilution of $b$ versus $\bar b$ tagging efficiency because of the presence of events with 4 $B$-mesons. The impact of multiple $B$-meson production is small unless the cross section for producing a single pair exceeds 1~mb. We show that even for larger values of the cross section the competing effects i) and ii) roughly compensate so that there is no loss in the precision with which CP-violating CKM angles can be determined.

hep-ph↗

arXiv1994

The High Energy Behavior of the Forward Scattering Parameters σtotal $ρ$, and $B$

Utilizing the most recent experimental data, we reanalyze high energy \pbar p and pp data, using two distinct (and {\em dissimilar}) analysis techniques: (1) asymptotic amplitude analysis, under the assumption that we have reached `asymptopia', and (2) an eikonal model whose amplitudes are designed to mimic real QCD amplitudes. The former gives strong evidence for a $\log \,(s/s_0)$ dependence at {\em current} energies and {\em not} $\log^2 (s/s_0)$, and demonstrates that odderons are {\em not} necessary to explain the experimental data. The latter gives a unitary model for extrapolation into true `asymptopia' from current energies, allowing us to predict the values of the total cross section at future supercolliders. Using our QCD-model, we obtain $\stot(16\,\, {\rm TeV})=109\pm4$\,mb and $\stot(40\,\, {\rm TeV})=124\pm4$\,mb.

hep-ph↗

arXiv1994

Particle Physics with High Energy Neutrinos

The topic of this review is the particle astrophysics of high energy neutrinos. High energy is defined as $E_ν > 100$~MeV. Main topics include: -- atmospheric neutrinos and muons from $π$, $K$ and charm decay. They probe uncharted territory in neutrino oscillations and constitute both the background and calibration of high energy neutrino telescopes, -- sources of high energy neutrino beams: the galactic plane, the sun, X-ray binaries, supernova remnants and interactions of extra-galactic cosmic rays with background photons, -- an extensive review of the mechanisms by which active galaxies may produce high energy particle beams, -- high energy neutrino signatures of cold dark matter and, -- a brief review of detection techniques (water and ice Cherenkov detectors, surface detectors, radio- and acoustic detectors, horizontal airshower arrays) and the instruments under construction.

hep-ph↗

arXiv1994

The Case for a Kilometer-Scale High Energy Neutrino Detector

Doing astronomy with photons of energies in excess of a GeV has turned out to be extremely challenging. Efforts are underway to develop instruments that may push astronomy to wavelengths smaller than $10^{-14}$~cm by mapping the sky in high energy neutrinos instead. Neutrino astronomy, born with the identification of thermonuclear fusion in the sun and the particle processes controlling the fate of a nearby supernova, will reach outside the galaxy and make measurements relevant to cosmology. The field is immersed in technology in the domains of particle physics to which many of its research goals are intellectually connected. To mind come the search for neutrino mass, cold dark matter (supersymmetric particles?) and the monopoles of the Standard Model. While a variety of collaborations are pioneering complementary methods by building telescopes with effective area in excess of 0.01~km$^2$, we show here that the natural scale of a high energy neutrino telescope is 1~km$^2$. With several thousand optical modules and a price tag unlikely to exceed 100 million dollars, the scope of a kilometer-scale instrument is similar to that of experiments presently being commissioned such as the SNO neutrino observatory in Canada and the Superkamiokande experiment in Japan.

hep-ph↗

arXiv1994

The Detection of Cold Dark Matter with Neutrino Telescopes

High energy neutrinos are produced by the annihilation of dark matter particles in our galaxy. These are presently searched for with large area, deep underground neutrino telescopes. Cold dark matter particles, trapped inside the sun, are an abundant source of such neutrinos. Back-of-the-envelope calculations are sufficient to demonstrate how neutrino telescopes are competitive with existing and future particle colliders such as the LHC in the search for weakly interacting massive cold dark matter particles. We will emphasize that a $1\,\rm km^2$ area is the natural scale for a future instrument capable of probing the full GeV--TeV mass range of cold dark matter particle candidates by searching for high energy neutrinos produced by their annihilation in the sun. We speculate on what such a detector may look like.

hep-ph↗

arXiv1994

The Indirect Detection of Halo Dark Matter

High energy particles are produced by the annihilation of dark matter particles in our galaxy. These are presently searched for using balloon-borne antiproton and positron detectors and large area, deep underground neutrino telescopes. Dark matter particles, trapped inside the sun, are an abundant source of such neutrinos. From both the cosmological and particle physics points of view the lightest, stable supersymmetric particle or neutralino is arguably the leading dark matter candidate. Its mass is bracketed by a minimum value of order a few tens of GeV, determined from unsuccessful accelerator searches, and a maximum value of order 1~TeV imposed by particle physics as well as cosmological constraints. Back-of-the-envelope calculations are sufficient to demonstrate how present neutrino telescopes are competitive with existing and future particle colliders such as the LHC in the search for supersymmetry. We emphasize that a $1\,\rm km^2$ area is the natural scale for a future instrument capable of probing the full GeV--TeV neutralino mass range by searching for high energy neutrinos produced by their annihilation in the sun.

hep-ph↗

arXiv1993

On the Precision of the Computation of the QCD Corrections to Electroweak Vacuum Polarizations

We demonstrate that the dispersive computation of the threshold enhancements to heavy quark vacuum polarizations is unstable. Because of the slow convergence of the dispersion relations the result critically depends on the intermediate energy region where the non-relativistic approximation, intrinsic to threshold calculations, is invalid. We discuss other ambiguities precluding a reliable calculation of the threshold contribution to the vacuum polarizations. In the absence of a solution prudence should force one to assign an error to the radiative corrections not far below the level of the pertubative O($αα_s$) contributions. This may preclude the extraction of the Higgs mass from precision measurements.

hep-ph↗

arXiv1993

Astroparticle Physics with High Energy Neutrino Telescopes

The first optical modules of the Baikal high energy neutrino telescope have recently been deployed. Commissioning of the AMANDA, DUMAND and NESTOR detectors will follow soon. Before discussing the detectors we review the arguments that pinpoint $0.1\rm~km^2$ as the natural scale of a neutrino telescope. Though present detectors do not quite reach this goal, their techniques, if successful, can be exploited to build km$^2$ detectors for a cost not exceeding one hundred million dollars. Motivations for the construction of km$^2$ deep underground detectors include i) neutrino astronomy and the search for cosmic accelerators, ii) neutrino oscillations using the atmospheric neutrino beam, iii) the search for neutrinos from the annihilation of dark matter particles in our galaxy, iv) the possibility to observe thermal neutrino emission from supernovae, and v) to make the serendipitous discovery. No astronomical telescope, detecting photons of any wavelength, has ever viewed sites in the Universe shielded by more than a few hundred grams of matter.

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