TRIUMF

About: TRIUMF is a facility organization based out in Vancouver, British Columbia, Canada. It is known for research contribution in the topics: Large Hadron Collider & Neutron. The organization has 3306 authors who have published 5770 publications receiving 212931 citations. The organization is also known as: TRI University Meson Facility.

Theoretical uncertainties for cosmological first-order phase transitions

Abstract: We critically examine the magnitude of theoretical uncertainties in perturbative calculations of fist-order phase transitions, using the Standard Model effective field theory as our guide. In the usual daisy-resummed approach, we find large uncertainties due to renormalisation scale dependence, which amount to two to three orders-of-magnitude uncertainty in the peak gravitational wave amplitude, relevant to experiments such as LISA. Alternatively, utilising dimensional reduction in a more sophisticated perturbative approach drastically reduces this scale dependence, pushing it to higher orders. Further, this approach resolves other thorny problems with daisy resummation: it is gauge invariant which is explicitly demonstrated for the Standard Model, and avoids an uncontrolled derivative expansion in the bubble nucleation rate.

Search for squarks and gluinos in final states with jets and missing transverse momentum at √s =13 TeV with the ATLAS detector

Abstract: A search for squarks and gluinos in final states containing hadronic jets, missing transverse momentum but no electrons or muons is presented. The data were recorded in 2015 by the ATLAS experiment ...

Precise measurement of the 7Be(p,gamma)8B S-factor

Abstract: We present new measurements of the $^{7}\mathrm{Be}(p,\ensuremath{\gamma})^{8}\mathrm{B}$ cross section from ${\overline{E}}_{\text{c.m.}}=116$ to $2460\phantom{\rule{0.3em}{0ex}}\text{keV}$ (where c.m. means center-of-mass), which incorporate several improvements over our previously published experiment, also discussed here. Our new measurements lead to ${S}_{17}(0)=22.1\ifmmode\pm\else\textpm\fi{}0.6(\mathrm{exp}\mathrm{t})\ifmmode\pm\else\textpm\fi{}0.6(\text{theor})\phantom{\rule{0.3em}{0ex}}\text{eV}\phantom{\rule{0.3em}{0ex}}\mathrm{b}$ based on data from ${\overline{E}}_{\text{c.m.}}=116$ to $362\phantom{\rule{0.3em}{0ex}}\text{keV}$, where the central value is based on the theory of Descouvemont and Baye. The theoretical error estimate is based on the fit of 12 different theories to our low-energy data. We compare our results to other ${S}_{17}(0)$ values extracted from both direct $[^{7}\mathrm{Be}(p,\ensuremath{\gamma})^{8}\mathrm{B}]$ and indirect (Coulomb-dissociation and heavy-ion reaction) measurements, and show that the results of these three types of experiments are not mutually compatible. We recommend a ``best'' value, ${S}_{17}(0)=21.4\ifmmode\pm\else\textpm\fi{}0.5(\mathrm{exp}\mathrm{t})\ifmmode\pm\else\textpm\fi{}0.6(\text{theor})\phantom{\rule{0.3em}{0ex}}\text{eV}\phantom{\rule{0.3em}{0ex}}\mathrm{b}$, based on the mean of all modern direct measurements below the ${1}^{+}$ resonance. We also present $S$ factors at $20\phantom{\rule{0.3em}{0ex}}\text{keV}$ which is near the center of the Gamow window: the result of our measurements is ${S}_{17}(20)=21.4\ifmmode\pm\else\textpm\fi{}0.6(\mathrm{exp}\mathrm{t})\ifmmode\pm\else\textpm\fi{}0.6(\text{theor})\phantom{\rule{0.3em}{0ex}}\text{eV}\phantom{\rule{0.3em}{0ex}}\mathrm{b}$, and the recommended value is ${S}_{17}(20)=20.6\ifmmode\pm\else\textpm\fi{}0.5(\mathrm{exp}\mathrm{t})\ifmmode\pm\else\textpm\fi{}0.6(\text{theor})\phantom{\rule{0.3em}{0ex}}\text{eV}\phantom{\rule{0.3em}{0ex}}\mathrm{b}$.

Measurement of the prompt J/ψ pair production cross-section in pp collisions at √s = 8 TeV with the ATLAS detector

Abstract: The production of two prompt $J/\psi$ mesons, each with transverse momenta $p_{\mathrm{T}}>8.5$ GeV and rapidity $|y| < 2.1$, is studied using a sample of proton-proton collisions at $\sqrt{s} = 8$ TeV, corresponding to an integrated luminosity of 11.4 fb$^{-1}$ collected in 2012 with the ATLAS detector at the LHC. The differential cross-section, assuming unpolarised $J/\psi$ production, is measured as a function of the transverse momentum of the lower-$p_{\mathrm{T}}$ $J/\psi$ meson, di-$J/\psi$ $p_{\mathrm{T}}$ and mass, the difference in rapidity between the two $J/\psi$ mesons, and the azimuthal angle between the two $J/\psi$ mesons. The fraction of prompt pair events due to double parton scattering is determined by studying kinematic correlations between the two $J/\psi$ mesons. The total and double parton scattering cross-sections are compared with predictions. The effective cross-section of double parton scattering is measured to be $\sigma_{\mathrm{eff}} = 6.3 \pm 1.6 \mathrm{(stat)} \pm 1.0 \mathrm{(syst)} \pm 0.1 \mathrm{(BF)} \pm 0.1 \mathrm{(lumi)}$ mb.

Measurement of the Higgs boson coupling properties in the H → ZZ ∗ → 4ℓ decay channel at √s=13 TeV with the ATLAS detector

Abstract: The coupling properties of the Higgs boson are studied in the four-lepton (e, μ) decay channel using 36.1 fb−1 of pp collision data from the LHC at a centre-of-mass energy of 13 TeV collected by the ATLAS detector. Cross sections are measured for the main production modes in several exclusive regions of the Higgs boson production phase space and are interpreted in terms of coupling modifiers. The inclusive cross section times branching ratio for H → ZZ∗ decay and for a Higgs boson absolute rapidity below 2.5 is measured to be 1. 73 − 0.23 + 0.24 (stat.) − 0.08 + 0.10 (exp.) ± 0.04(th.) pb compared to the Standard Model prediction of 1.34±0.09 pb. In addition, the tensor structure of the Higgs boson couplings is studied using an effective Lagrangian approach for the description of interactions beyond the Standard Model. Constraints are placed on the non-Standard-Model CP-even and CP-odd couplings to Z bosons and on the CP-odd coupling to gluons.