7,135 research outputs found
Transverse momentum distribution of vector mesons produced in ultraperipheral relativistic heavy ion collisions
We study the transverse momentum distribution of vector mesons produced in
ultraperipheral relativistic heavy ion collisions (UPCs). In UPCs there is no
strong interaction between the nuclei and the vector mesons are produced in
photon-nucleus collisions where the (quasireal) photon is emitted from the
other nucleus. Exchanging the role of both ions leads to interference effects.
A detailed study of the transverse momentum distribution which is determined by
the transverse momentum of the emitted photon, the production process on the
target and the interference effect is done. We study the total unrestricted
cross section and those, where an additional electromagnetic excitation of one
or both of the ions takes place in addition to the vector meson production, in
the latter case small impact parameters are emphasized.Comment: 12 pages, REVTeX manuscrip
Searching for t-bar t Resonances at the Large Hadron Collider
Many new physics models predict resonances with masses in the TeV range which
decay into a pair of top quarks. With its large cross section, t-bar t
production at the Large Hadron Collider (LHC) offers an excellent opportunity
to search for such particles. We present a detailed study of the discovery
potential of the CERN Large Hadron Collider for Kaluza-Klein (KK) excitations
of the gluon in bulk Randall-Sundrum (RS) models in the t-bar t -> ell^+/- nu
b-bar bq-bar q' (ell=e, mu) final state. We utilize final states with one or
two tagged b-quarks, and two, three or four jets (including b-jets). Our
calculations take into account the finite resolution of detectors, the energy
loss due to b-quark decays, the expected reduced b-tagging efficiency at large
t-bar t invariant masses, and include the background originating from Wb-bar
b+jets, (Wb+W-bar b)+jets, W+jets, and single top + jets production. We derive
semi-realistic 5 sigma discovery limits for nine different KK gluon scenarios,
and compare them with those for KK gravitons, and a Z_H boson in the Littlest
Higgs model. We also analyze the capabilities of the LHC experiments to
differentiate between individual KK gluon models and measure the couplings of
KK gluons to quarks. We find that, for the parameters and models chosen, KK
gluons with masses up to about 4 TeV can be discovered at the LHC. The ability
of the LHC to discriminate between different bulk RS models, and to measure the
couplings of the KK gluons is found to be highly model dependent.Comment: revtex3, 27 pages, 5 tables, 6 figure
Role of Higher Multipole Excitations in the Electromagnetic Dissociation of One Neutron Halo Nuclei
We investigate the role of higher multipole excitations in the
electromagnetic dissociation of one-neutron halo nuclei within two different
theoretical models -- a finite range distorted wave Born approximation and
another in a more analytical method with a finite range potential. We also
show, within a simple picture, how the presence of a weakly bound state affects
the breakup cross section.Comment: 8 pages, 9 figure
Getting Cars Off the Road: The Cost-Effectiveness of an Episodic Pollution Control Program
Ground level ozone remains a serious problem in the United States. Because ozone non-attainment is a summer problem, episodic rather than continuous controls of ozone precursors are possible. We evaluate the costs and effectiveness of an episodic scheme that requires people to buy permits in order to drive on high ozone days. We estimate the demand function for permits based on a survey of 1,300 households in the Washington, DC metropolitan area. Assuming that all vehicle owners comply with the scheme, the permit program would reduce VOCs by 50 tons and NOx by 42 tons per Code Red day at a permit price of 9 million (2008 USD). This compares favorably with permanent methods of reducing VOCs that cost $645 per ton per year.Ground-Level Ozone, Episodic Pollution Control Schemes, Mobile Sources, Volatile Organic Compounds (Vocs), Cost Per Ton of Vocs Removed
Vector Boson Pair Production in Hadronic Collisions at Order : Lepton Correlations and Anomalous Couplings
We present cross sections for production of electroweak vector boson pairs,
, and , in and collisions, at next-to-leading
order in . We treat the leptonic decays of the bosons in the
narrow-width approximation, but retain all spin information via decay angle
correlations. We also include the effects of and anomalous
couplings.Comment: 23 pages, 8 figures, 3 table
Waist-to-height ratio and cardiometabolic risk factors in adolescence: findings from a prospective birth cohort
What is already known about this subject
In adults, associations between body mass index (BMI), waist-to-height ratio (WHtR) and cardiometabolic outcomes are similar.
In children and adolescents, results from cross-sectional studies examining the associations between BMI z scores, WHtR and cardiometabolic outcomes are conflicting and there is a paucity of prospective data.<p></p>
What this study adds
This is the first study to demonstrate the prospective association between WHtR in childhood and cardiometabolic outcomes in adolescent boys.
WHtR is a simple calculation that can be used to identify children and adolescents for cardiometabolic risk without the need for reference growth charts.
The WHtR cut-point of â„0.5 was highly specific in identifying cardiometabolic risk co-occurrence but has poor sensitivity.<p></p>
Objective
To examine the associations between body mass index (BMI) and waist-to-height ratio (WHtR) measured in childhood and adolescence and cardiometabolic risk factors in adolescence.<p></p>
Methods
Secondary data analysis of the Avon Longitudinal Study of Parents and Children, a population based cohort. Data from 2858 adolescents aged 15.5 (standard deviation 0.4) years and 2710 of these participants as children aged 7â9 years were used in this analysis. Outcome measures were cardiometabolic risk factors, including triglycerides, low density lipoprotein cholesterol, high density lipoprotein cholesterol, insulin, glucose and blood pressure at 15 years of age.<p></p>
Results
Both BMI and WHtR measured at ages 7â9 years and at age 15 years were associated with cardiometabolic risk factors in adolescents. A WHtR â„0.5 at 7â9 years increased the odds by 4.6 [95% confidence interval 2.6 to 8.1] for males and 1.6 [0.7 to 3.9] for females of having three or more cardiometabolic risk factors in adolescence. Cross-sectional analysis indicated that adolescents who had a WHtR â„0.5, the odds ratio of having three or more cardiometabolic risk factors was 6.8 [4.4 to 10.6] for males and 3.8 [2.3 to 6.3] for females. The WHtR cut-point was highly specific in identifying cardiometabolic risk co-occurrence in male children and adolescents as well as female children (90 to 95%), but had poor sensitivity (17 to 53%). Similar associations were observed when BMI was used to define excess adiposity.<p></p>
Conclusions
WHtR is a simple alternative to age and sex adjusted BMI for assessing cardiometabolic risk in adolescents
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