arXiv subjects

M. H. Reno

Publications and source records attributed to M. H. Reno.

51 records · Page 3Linked to original sources

arXiv1998

Lepton Fluxes from Atmospheric Charm

We reexamine the charm contribution to atmospheric lepton fluxes in the context of perturbative QCD. We include next-to-leading order corrections and discuss theoretical uncertainties due to the extrapolations of the gluon distributions at small-x. We show that the charm contribution to the atmospheric muon flux becomes dominant over the conventional contribution from pion and kaon decays at energies of about 10^5 GeV. We compare our fluxes with previous calculations.

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arXiv1997

Structure Function Subgroup Summary

We summarize the studies and discussions of the Structure Function subgroup of the QCD working group of the Snowmass 1996 Workshop: New Directions for High Energy Physics.

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arXiv1997

Muon and Muon Neutrino Fluxes from Atmospheric Charm

The charm contribution to the atmospheric fluxes of muons and muon neutrinos may be enhanced by as much as a factor of 10 when one includes the contributions of D->pi,K->leptons and folds in uncertainties in the charm cross section and energy distribution. In the energy range considered here, from 100 GeV to 10 TeV, the charm contribution is small compared to the conventional flux of muons and muon neutrinos.

hep-ph↗

arXiv1997

Secondary Decays in Atmospheric Charm Contributions to the Flux of Muons and Muon Neutrinos

We present a calculation of the fluxes of muons and muon neutrinos from the decays of pions and kaons that are themselves the decay products of charmed particles produced in the atmosphere by cosmic ray-air collisions. Using the perturbative cross section for charm production, these lepton fluxes are two to three orders of magnitude smaller than the fluxes from the decays of pions and kaons directly produced in cosmic ray-air collisions. Intrinsic charm models do not significantly alter our conclusions, nor do models with a charm cross section enhanced in the region above an incident cosmic ray energy of 1 TeV.

hep-ph↗

arXiv1997

Z polarization in the Higgs boson signal at the LHC

We examine a method of studying the Z polarization in $H\to ZZ \to \ell^+ \ell^- ν\barν$ in proton-proton collisions at the Large Hadron Collider (LHC). Included are the dominant contributions: gluon fusion production of the Higgs boson, continuum production of Z pairs, and the Z+missing jet QCD background. The polarization signal is distinguishable from the background for Higgs masses less than or equal to $\sim 700$ GeV, for an integrated luminosity of 10^5 pb^{-1}.

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arXiv1996

Detecting Neutrinos from AGNs and Topological Defects with Neutrino Telescopes

We evaluate neutrino-nucleon cross section for energies up to $10^{21} eV$ in light of new information on the small-$x$ behavior of parton distributions. We give predictions for large underground neutrino telescope event rates for ultrahigh-energy neutrinos from Active Galactic Nuclei and from the decay of topological defects formed in the early Universe.

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arXiv1996

Ultrahigh-Energy Neutrino Interactions and Neutrino Telescope Event Rates

We present results for neutrino-nucleon cross sections for energies up to 10$^21$eV, of relevance to the detection of ultrahigh energy galactic and extragalactic neutrinos. At the highest energies, our results are about 2.4 times larger than previous estimates. Using these new cross sections, we predict neutrino telescope event rates for the upward moving muons initiated by the neutrino interactions in the Earth and for contained-vertex events in the PeV range due to neutrino-electron interactions. We show that future neutrino detectors, such as AMANDA, BAIKAL, DUMAND and NESTOR have a very good chance of detecting neutrinos which originate in the Active Galactic Nuclei.

hep-ph↗

arXiv1996

New Predictions for Neutrino Telescope Event Rates

Recent measurements of the small-$x$ deep-inelastic regime at HERA translate to new expectations for the neutrino-nucleon cross section at ultrahigh energies. We present event rates for large underground neutrino telescopes based on the new cross section for a variety of models of neutrino production in Active Galactic Nuclei, and we compare these rates with earlier cross section calculations.

hep-ph↗

arXiv1995

Small-x Parton Densities from HERA and the Ultra-High Energy Neutrino-Nucleon Cross Sections

In light of recent measurements of the nucleon structure function in the small-$x$ deep-inelastic regime at HERA and the consequently improved theoretical understanding of the quark distributions in this range of parton fractional momentum, we present new results for the neutrino-nucleon cross section at ultra high energies, up to $ E_ν \sim 10^{21}$ eV. The results are relevant to deep underground muon detectors looking for such neutrinos. For $\simeq 10^{20}$ eV neutrinos, our cross sections are about a factor of $4$ to $10$ times larger than the previously reported results by Reno, Quigg and Walker. We discuss implications of this new neutrino-nucleon cross section for a variety of current and future neutrino detectors.

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arXiv1994

$Z$ POLARIZATION IN $pp\rightarrow ZZ\rightarrow \ell^+\ell^-ν\barν$ AT THE LHC

We evaluate the feasibility of measuring the $Z$ polarization from a heavy Higgs signal in the decay channel $H\rightarrow ZZ \rightarrow \ell^+ \ell^-ν\barν$. Including gluon fusion production of the Higgs, continuum production of $Z$ pairs and the QCD background of single $Z$ production with a missing jet, we find that the average value of a new variable to measure the $Z$ polarization, as a function of transverse mass, will demonstrate the existence of a Higgs boson for heavy Higgs masses up to 800 GeV at the LHC with an integrated luminosity of 10$^5$ pb$^{-1}$.

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arXiv1994

Hadron collider limits on anomalous $WWγ$ couplings

A next-to-leading log calculation of the reactions $pp$ and $p\overline{p}\rightarrow W^\pmγX$ is presented including a tri-boson gauge coupling from non-Standard Model contributions. Two approaches are made for comparison. The first approach considers the tri-boson $WWγ$ coupling as being uniquely fixed by tree level unitarity at high energies to its Standard Model form and, consequently, suppresses the non-Standard Model contributions with form factors. The second approach is to ignore such considerations and calculate the contributions to non-Standard Model tri-boson gauge couplings without such suppressions. It is found that at Tevatron energies, the two approaches do not differ much in quantitative results, while at Large Hadron Collider (LHC) energies the two approaches give significantly different predictions for production rates. At the Tevatron and LHC, however, the sensitivity limits on the anomalous coupling of $WWγ$ are too weak to usefully constrain parameters in effective Lagrangian models.

hep-ph↗

arXiv1994

Relative distributions of W's and Z's at low transverse momenta

Despite large uncertainties in the $W^\pm$ and $Z^0$ transverse momentum ($q_T$) distributions for $q_T\lsim 10$ GeV, the ratio of the distributions varys little. The uncertainty in the ratio of $W$ to $Z$ $q_T$ distributions is on the order of a few percent, independent of the details of the nonperturbative parameterization.

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arXiv1993

Report of the Subgroup on the Top Quark

The top group studied discovery issues as well as measurements to be made at the Tevatron, the LHC and the SSC.

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arXiv1993

An Estimate of Jet Activity in $t\bar t$ Events

We present a calculation of jet activity associated with pair production of top quarks at hadron colliders and supercolliders. Our approach is based upon a merger of $2\rightarrow 3$ matrix elements with initial and final state parton showers. We tabulate expected multi-jet rates in $t\bar t$ events, and compare with ${\cal O}(α_s^3 )$ matrix element results and parton showers based upon $2\rightarrow 2$ subprocesses. The merged calculation includes the correct matrix element for the first leg of the parton shower, but also includes the effects of approximate all-orders quark and gluon emission. We also evaluate expected jet activity in top pair events at hadron supercolliders; in particular, a comparison of the jet activity in the far forward region is made. It is found that the merged calculation yields more jet activity in the forward region than pure matrix element estimates, but also more jet activity in the central region. This can be important for background calculations to $H\rightarrow WW$ and strong $WW$ scattering processes.

hep-ph↗

arXiv1993

Enhancing the Higgs signal in $pp\rightarrow ZZ\rightarrow \ell^+\ell^-ν\barν$

One of the possible modes suggested for detecting the Higgs particle is $pp\rightarrow ZZ\rightarrow\ell^+\ell^-ν\barν$, where the Higgs appears as a resonance on a Jacobian background. Unfortunately there are QCD background processes which mimic the final state and we are obliged to impose stringent kinematic cuts to remove them. However, in doing so we also remove a significant fraction of the signal. In this report we suggest a method, based on examining the distribution of the final state charged leptons, which could allow us to relax our cuts and thus salvage the signal.

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