371 research outputs found
Metadynamics surfing on topology barriers: the CP N 121 case
As one approaches the continuum limit, QCD systems, investigated via numerical simulations, remain trapped in sectors of field space with fixed topological charge. As a consequence the numerical studies of physical quantities may give biased results. The same is true in the case of two dimensional CPN 121 models. In this paper we show that metadynamics, when used to simulate CPN 121, allows to address efficiently this problem. By studying CP20 we show that we are able to reconstruct the free energy of the topological charge F (Q) and compute the topological susceptibility as a function of the coupling and of the volume. This is a very important physical quantity in studies of the dynamics of the \u3b8 vacuum and of the axion. This method can in principle be extended to QCD applications. \ua9 2016, The Author(s)
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Search for lepton-flavour-violating decays of Higgs-like bosons.
A search is presented for a Higgs-like boson with mass in the range 45 to 195 GeV/c2 decaying into a muon and a tau lepton. The dataset consists of proton-proton interactions at a centre-of-mass energy of 8 TeV , collected by the LHCb experiment, corresponding to an integrated luminosity of 2 fb-1 . The tau leptons are reconstructed in both leptonic and hadronic decay channels. An upper limit on the production cross-section multiplied by the branching fraction at 95% confidence level is set and ranges from 22 pb for a boson mass of 45 GeV/c2 to 4 pb for a mass of 195 GeV/c2
How much choice is there in housing choice vouchers? Neighborhood risk and free market rental housing accessibility for active drug users in Hartford, Connecticut
<p>Abstract</p> <p>Background</p> <p>Since the mid-1970s, the dominant model for U.S. federal housing policy has shifted from unit-based programs to tenant based vouchers and certificates, intended to allow recipients a choice in their housing and neighborhoods. Surprisingly little research has examined the question of where those with Section 8 housing vouchers are able to live, but some research suggests that voucher holders are more likely to reside in distressed neighborhoods than unsubsidized renter households. Further, federal housing policy has limited drug users' access to housing subsidies. In turn, neighborhood disorder has been associated with higher levels of injection drug risk behaviors, and higher drug-related mortality. This paper explores rental accessibility and neighborhood characteristics of advertised rental housing in Hartford CT.</p> <p>Methods</p> <p>Brief telephone interviews were conducted with landlords or management companies with units to rent in Hartford to explore housing accessibility measured as initial move in costs, credit and criminal background checks, and whether rental subsidies were accepted. These data were supplemented with in-depth interviews with landlords, shelter staff and active users of heroin, crack or cocaine. Apartments for rent were geocoded and mapped using <b>ArcGIS</b>. We used location quotients to identify areas where low-income rental housing is concentrated. Finally, we mapped apartments in relation to drug and violent arrest rates in each neighborhood.</p> <p>Results</p> <p>High security deposits, criminal background and credit checks limit housing accessibility even for drug users receiving vouchers. While most landlords or management companies accepted housing subsidies, several did not. Voucher units are concentrated in neighborhoods with high poverty neighborhoods. Landlords reported little incentive to accept rental subsidies in neighborhoods with low crime rates, but appreciated the guarantee provided by Section 8 in high crime neighborhoods that were less likely to attract applicants with good jobs and credit.</p> <p>Conclusion</p> <p>Housing vouchers in themselves do not greatly improve recipients' choice of neighborhood and voucher units are concentrated in the most distressed neighborhoods. Policy changes are needed to increase landlords' incentives to accept housing subsidies. Interventions to improve neighborhood conditions are needed to improve the probability of success for those recovering from drug addictions.</p
Production of phi mesons at mid-rapidity in sqrt(s_NN) = 200 GeV Au+Au collisions at RHIC
We present the first results of meson production in the K^+K^- decay channel
from Au+Au collisions at sqrt(s_NN) = 200 GeV as measured at mid-rapidity by
the PHENIX detector at RHIC. Precision resonance centroid and width values are
extracted as a function of collision centrality. No significant variation from
the PDG accepted values is observed. The transverse mass spectra are fitted
with a linear exponential function for which the derived inverse slope
parameter is seen to be constant as a function of centrality. These data are
also fitted by a hydrodynamic model with the result that the freeze-out
temperature and the expansion velocity values are consistent with the values
previously derived from fitting single hadron inclusive data. As a function of
transverse momentum the collisions scaled peripheral.to.central yield ratio RCP
for the is comparable to that of pions rather than that of protons. This result
lends support to theoretical models which distinguish between baryons and
mesons instead of particle mass for explaining the anomalous proton yield.Comment: 326 authors, 24 pages text, 23 figures, 6 tables, RevTeX 4. To be
submitted to Physical Review C as a regular article. Plain text data tables
for the points plotted in figures for this and previous PHENIX publications
are (or will be) publicly available at http://www.phenix.bnl.gov/papers.htm
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Updated measurement of time-dependent CP -violating observables in Bs0→J/ψ<sup>K+</sup><sup>K-</sup> decays
The decay-time-dependent asymmetry in
decays is measured using proton-proton collision data, corresponding to an
integrated luminosity of , collected with the LHCb
detector at a centre-of-mass energy of in 2015 and 2016.
Using a sample of approximately 117\,000 signal decays with an invariant mass in the vicinity of the resonance, the -violating
phase is measured, along with the difference in decay widths of the
light and heavy mass eigenstates of the - system,
. The difference of the average and meson
decay widths, , is determined using in addition a sample of
decays. The values obtained are , and , where the first uncertainty is statistical and the
second systematic. These are the most precise single measurements of these
quantities to date and are consistent with expectations based on the Standard
Model and with a previous LHCb analysis of this decay using data recorded at
centre-of-mass energies 7 and 8 TeV. Finally, the results are combined with
recent results from decays obtained using
the same dataset as this analysis, and with previous independent LHCb results
Social, Structural and Behavioral Determinants of Overall Health Status in a Cohort of Homeless and Unstably Housed HIV-Infected Men
Background: Previous studies indicate multiple influences on the overall health of HIV-infected persons; however, few assess and rank longitudinal changes in social and structural barriers that are disproportionately found in impoverished populations. We empirically ranked factors that longitudinally impact the overall health status of HIV-infected homeless and unstably housed men. Methods and Findings: Between 2002 and 2008, a cohort of 288 HIV+ homeless and unstably housed men was recruited and followed over time. The population was 60 % non-Caucasian and the median age was 41 years; 67 % of study participants reported recent drug use and 20 % reported recent homelessness. At baseline, the median CD4 cell count was 349 cells/ml and 18 % of eligible persons (CD4,350) took antiretroviral therapy (ART). Marginal structural models were used to estimate the population-level effects of behavioral, social, and structural factors on overall physical and mental health status (measured by the SF-36), and targeted variable importance (tVIM) was used to empirically rank factors by their influence. After adjusting for confounding, and in order of their influence, the three factors with the strongest negative effects on physical health were unmet subsistence needs, Caucasian race, and no reported source of instrumental support. The three factors with the strongest negative effects on mental health were unmet subsistence needs, not having a close friend/confidant, and drug use. ART adherence.90 % ranked 5th for its positive influence on mental health, and viral loa
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Measurement of CP observables in the process B <sup>0</sup> → DK <sup>*0</sup> with two- and four-body D decays
Measurements of observables in decays are presented,
where represents a superposition of and states. The
meson is reconstructed in the two-body final states , ,
and , and, for the first time, in the four-body final
states , and .
The analysis uses a sample of neutral mesons produced in proton-proton
collisions, corresponding to an integrated luminosity of 1.0, 2.0 and 1.8 collected with the LHCb detector at centre-of-mass energies of
7, 8 and 13 TeV, respectively. First observations of the decays
and are
obtained. The measured observables are interpreted in terms of the
-violating weak phase
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Observation of the Λb0→χc1 (3872) pK<sup>−</sup> decay
Using proton-proton collision data, collected with the LHCb detector and
corresponding to 1.0, 2.0 and 1.9fb of integrated luminosity at the
centre-of-mass energies of 7, 8, and 13 TeV, respectively, the decay
with is
observed for the first time. The significance of the observed signal is in
excess of seven standard deviations. It is found that of the
decays proceed via the two-body intermediate state
. The~branching fraction with respect to that of
the decay mode, where the
~meson is reconstructed in the final state, is
measured to be: \begin{equation*}
\frac{\Lambda_b^0\to\chi_{c1}(3872)pK^-}{\Lambda_b\to\psi(2S)p K^-} \times
\frac{\mathcal{B}(\chi_{c1} \to J/\psi \pi^+\pi^-)}{\mathcal{B}(\psi(2S)\to
J/\psi \pi^+\pi^-)} = \left(5.4 \pm 1.1 \pm 0.2\right)\times 10^{-2}\,,
\end{equation*} where the first uncertainty is statistical and the second is
systematic
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