arXiv subjects

C. Hill

Publications and source records attributed to C. Hill.

42 records · Page 3Linked to original sources

arXiv2011

Boosted objects: a probe of beyond the Standard Model physics

We present the report of the hadronic working group of the BOOST2010 workshop held at the University of Oxford in June 2010. The first part contains a review of the potential of hadronic decays of highly boosted particles as an aid for discovery at the LHC and a discussion of the status of tools developed to meet the challenge of reconstructing and isolating these topologies. In the second part, we present new results comparing the performance of jet grooming techniques and top tagging algorithms on a common set of benchmark channels. We also study the sensitivity of jet substructure observables to the uncertainties in Monte Carlo predictions.

hep-ph↗

arXiv2010

Scaling of the F_2 structure function in nuclei and quark distributions at x>1

We present new data on electron scattering from a range of nuclei taken in Hall C at Jefferson Lab. For heavy nuclei, we observe a rapid falloff in the cross section for $x>1$, which is sensitive to short range contributions to the nuclear wave-function, and in deep inelastic scattering corresponds to probing extremely high momentum quarks. This result agrees with higher energy muon scattering measurements, but is in sharp contrast to neutrino scattering measurements which suggested a dramatic enhancement in the distribution of the `super-fast' quarks probed at x>1. The falloff at x>1 is noticeably stronger in ^2H and ^3He, but nearly identical for all heavier nuclei.

nucl-ex↗

arXiv2009

New measurements of the EMC effect in very light nuclei

New Jefferson Lab data are presented on the nuclear dependence of the inclusive cross section from 2H, 3He, 4He, 9Be and 12C for 0.3<x<0.9, Q^2 approximately 3-6 GeV^2. These data represent the first measurement of the EMC effect for 3He at large x and a significant improvement for 4He. The data do not support previous A-dependent or density-dependent fits to the EMC effect and suggest that the nuclear dependence of the quark distributions may depend on the local nuclear environment.

nucl-ex↗

arXiv2008

Measurement of the Top Quark Mass using Quantities with Minimal Dependence on the Jet Energy Scale

We present three measurements of the top quark mass in the lepton plus jets channel with 1.9 fb-1 of data using quantities with minimal dependence on the jet energy scale in the lepton plus jets channel at CDF. One measurement uses the mean transverse decay length of b-tagged jets (L2d) to determine the top mass, another uses the transverse momentum of the lepton (LepPt) to determine the top mass, and a third measurement uses both variables simultaneously. Using the L2d variable we measure a top mass of 176.7 (+10.0) (-8.9) (stat) +/- 3.4 (syst) GeV/c^2, using the LepPt variable we measure a top mass of 173.5 (+8.9) (-9.1) (stat) +/- 4.2 (syst) GeV/c^2, and doing the combined measurement using both variables we arrive at a top mass result of 175.3 +/- 6.2 (stat) +/- 3.0 (syst) GeV/c^2. Since some of the systematic uncertainties are statistically limited, these results are expected to improve significantly if more data is added at the Tevatron in the future, or if the measurement is done at the LHC.

hep-ex↗

arXiv2007

The electronic bands of CrD, CrH, MgD and MgH: application to the "deuterium test"

We compute opacities for the electronic molecular band systems A 6Sigma+ -- X 6Sigma+ of CrH and CrD, and A 2Pi -- X 2Sigma+ of MgH and MgD. The opacities are computed by making use of existing spectroscopic constants for MgH and CrH. These constants are adjusted for the different reduced masses of MgD and CrD. Frank-Condon factors are used to provide intensities for the individual vibronic bands. These results are used in the computation of synthetic spectra between Tef = 1800 and 1200 K with an emphasis on the realisation of ``deuterium test'', first proposed by Bejar et al. (1999) to distinguish brown dwarfs from planetary mass objects. We discuss the possible use of CrD and MgD electronic bands for the "deuterium test". We find CrD to be the more promising of the two deuterides, potentially, the most useful bands of CrH/CrD are the Delta v = +1 and Delta v = -1 at 0.795 and 0.968 micron.

astro-ph↗

arXiv1995

Cosmology with Ultra-light Pseudo-Nambu-Goldstone Bosons

We explore the cosmological implications of an ultra-light pseudo-Nambu-Goldstone boson. With global spontaneous symmetry breaking scale $f \simeq 10^{18}$ GeV and explicit breaking scale comparable to MSW neutrino masses, $M \sim 10^{-3}$ eV, such a field, which acquires a mass $m_ϕ\sim M^2/f \sim H_0$, would have become dynamical at recent epochs and currently dominate the energy density of the universe. The field acts as an effective cosmological constant for several expansion times and then relaxes into a condensate of coherent non-relativistic bosons. Such a model can reconcile dynamical estimates of the density parameter, $Ω_m \sim 0.2$, with a spatially flat universe, and can yield an expansion age $H_0 t_0 \simeq 1$ while remaining consistent with limits from gravitational lens statistics.

astro-ph↗