Measurements of differential and double-differential Drell-Yan cross sections in proton-proton collisions at [Formula: see text][Formula: see text]

Mental health outcomes of family carers after admission to aged care: A cross-sectional survey study

OBJECTIVES

This study investigated the predictors of poor mental health outcomes among family carers of residents after transitioning into residential aged care.

METHODS

Using a cross-sectional design, five groups of variables were evaluated as predictors: caregiver demographics; caregiving load; resident-related variables; loneliness and visiting frequency; and the impact of the COVID-19 context. A total of 309 primary family contacts of all residents of two residential aged care organisations in the state of Victoria (Australia) participated in the study (response rate 19%). The K-10 and the Burden Scale for Family Caregivers were used to measure the primary outcomes. We compared psychological distress and burden outcomes between carers whose relative was admitted within the last 12 months, or longer than 12 months ago.

RESULTS

Time since admission (<12 months or >12 months) did not affect the level of psychological distress (t (238) = -.08, p = .94) or subjective burden (t (245) = -.89, p = .38). Being a woman, a spouse, speaking a language other than English at home, being less satisfied with the support offered by the facility, not feeling supported in the decision to admit their relative, being lonely and providing higher levels of care preadmission were predictors of poor mental health outcomes.

CONCLUSIONS

Older women with low-English proficiency who were primary carers and are socially isolated, are more likely to experience poor mental health outcomes and need additional support. These findings may inform the development of screening tools and tailored interventions to support this population during and after the transition process.

Measurement of the mass dependence of the transverse momentum of lepton pairs in Drell-Yan production in proton-proton collisions at s=13TeV

The double differential cross sections of the Drell-Yan lepton pair (ℓ + ℓ - , dielectron or dimuon) production are measured as functions of the invariant mass m ℓ ℓ , transverse momentum p T ( ℓ ℓ ) , and φ η ∗ . The φ η ∗ observable, derived from angular measurements of the leptons and highly correlated with p T ( ℓ ℓ ) , is used to probe the low-p T ( ℓ ℓ ) region in a complementary way. Dilepton masses up to 1Te V are investigated. Additionally, a measurement is performed requiring at least one jet in the final state. To benefit from partial cancellation of the systematic uncertainty, the ratios of the differential cross sections for various m ℓ ℓ ranges to those in the Z mass peak interval are presented. The collected data correspond to an integrated luminosity of 36.3fb - 1 of proton-proton collisions recorded with the CMS detector at the LHC at a centre-of-mass energy of 13Te V . Measurements are compared with predictions based on perturbative quantum chromodynamics, including soft-gluon resummation.

Parton distributions with small-x resummation: evidence for BFKL dynamics in HERA data

We present a determination of the parton distribution functions of the proton in which NLO and NNLO fixed-order calculations are supplemented by NLLx small-x resummation. Deep-inelastic structure functions are computed consistently at NLO+NLL x or NNLO+NLL x , while for hadronic processes small-x resummation is included only in the PDF evolution, with kinematic cuts introduced to ensure the fitted data lie in a region where the fixed-order calculation of the hard cross-sections is reliable. In all other respects, the fits use the same methodology and are based on the same global dataset as the recent NNPDF3.1 analysis. We demonstrate that the inclusion of small-x resummation leads to a quantitative improvement in the perturbative description of the HERA inclusive and charm-production reduced cross-sections in the small x region. The impact of the resummation in our fits is greater at NNLO than at NLO, because fixed-order calculations have a perturbative instability at small x due to large logarithms that can be cured by resummation. We explore the phenomenological implications of PDF sets with small-x resummation for the longitudinal structure function F L at HERA, for parton luminosities and LHC benchmark cross-sections, for ultra-high-energy neutrino-nucleus cross-sections, and for future high-energy lepton-proton colliders such as the LHeC.

Parton distributions in the LHC era

Analyses of LHC (and other!) experiments require robust and statistically accurate determinations of the structure of the proton, encoded in the parton distribution functions (PDFs). The standard description of hadronic processes relies on factorization theorems, which allow a separation of process-dependent short-distance physics from the universal long-distance structure of the proton. Traditionally the PDFs are obtained from fits to experimental data. However, understanding the long-distance properties of hadrons is a nonperturbative problem, and lattice QCD can play a role in providing useful results from first principles. In this talk we compare the different approaches used to determine PDFs, and try to assess the impact of existing, and future, lattice calculations.

Catching a New Force by the Tail

The Large Hadron Collider (LHC) is sensitive to new heavy gauge bosons that produce narrow peaks in the dilepton invariant mass spectrum up to about m_{Z^{'}}∼5  TeV Z^{'}s that are too heavy to produce directly can reveal their presence through interference with standard model dilepton production. We show that the LHC can significantly extend the mass reach for such Z^{'}s by performing precision measurements of the shape of the dilepton invariant mass spectrum. The high-luminosity LHC can exclude, with 95% confidence, new gauge bosons as heavy as m_{Z^{'}}∼10-20  TeV that couple with gauge coupling strength of g_{Z^{'}}∼1-2.

Parton distributions from high-precision collider data: NNPDF Collaboration

We present a new set of parton distributions, NNPDF3.1, which updates NNPDF3.0, the first global set of PDFs determined using a methodology validated by a closure test. The update is motivated by recent progress in methodology and available data, and involves both. On the methodological side, we now parametrize and determine the charm PDF alongside the light-quark and gluon ones, thereby increasing from seven to eight the number of independent PDFs. On the data side, we now include the D0 electron and muon W asymmetries from the final Tevatron dataset, the complete LHCb measurements of W and Z production in the forward region at 7 and 8 TeV, and new ATLAS and CMS measurements of inclusive jet and electroweak boson production. We also include for the first time top-quark pair differential distributions and the transverse momentum of the Z bosons from ATLAS and CMS. We investigate the impact of parametrizing charm and provide evidence that the accuracy and stability of the PDFs are thereby improved. We study the impact of the new data by producing a variety of determinations based on reduced datasets. We find that both improvements have a significant impact on the PDFs, with some substantial reductions in uncertainties, but with the new PDFs generally in agreement with the previous set at the one-sigma level. The most significant changes are seen in the light-quark flavor separation, and in increased precision in the determination of the gluon. We explore the implications of NNPDF3.1 for LHC phenomenology at Run II, compare with recent LHC measurements at 13 TeV, provide updated predictions for Higgs production cross-sections and discuss the strangeness and charm content of the proton in light of our improved dataset and methodology. The NNPDF3.1 PDFs are delivered for the first time both as Hessian sets, and as optimized Monte Carlo sets with a compressed number of replicas.

The photon PDF from high-mass Drell-Yan data at the LHC

Achieving the highest precision for theoretical predictions at the LHC requires the calculation of hard-scattering cross sections that include perturbative QCD corrections up to (N)NNLO and electroweak (EW) corrections up to NLO. Parton distribution functions (PDFs) need to be provided with matching accuracy, which in the case of QED effects involves introducing the photon parton distribution of the proton, [Formula: see text]. In this work a determination of the photon PDF from fits to recent ATLAS measurements of high-mass Drell-Yan dilepton production at [Formula: see text] TeV is presented. This analysis is based on the xFitter framework, and has required improvements both in the APFEL program, to account for NLO QED effects, and in the aMCfast interface to account for the photon-initiated contributions in the EW calculations within MadGraph5_aMC@NLO. The results are compared with other recent QED fits and determinations of the photon PDF, consistent results are found.

Precision measurement and interpretation of inclusive W+ , W- and Z/γ∗ production cross sections with the ATLAS detector

High-precision measurements by the ATLAS Collaboration are presented of inclusive W + → ℓ + ν , W - → ℓ - ν ¯ and Z / γ ∗ → ℓ ℓ ( ℓ = e , μ ) Drell-Yan production cross sections at the LHC. The data were collected in proton-proton collisions at s = 7 TeV with an integrated luminosity of 4.6 fb - 1 . Differential W + and W - cross sections are measured in a lepton pseudorapidity range | η ℓ | < 2.5 . Differential Z / γ ∗ cross sections are measured as a function of the absolute dilepton rapidity, for | y ℓ ℓ | < 3.6 , for three intervals of dilepton mass, m ℓ ℓ , extending from 46 to 150 GeV . The integrated and differential electron- and muon-channel cross sections are combined and compared to theoretical predictions using recent sets of parton distribution functions. The data, together with the final inclusive e ± p scattering cross-section data from H1 and ZEUS, are interpreted in a next-to-next-to-leading-order QCD analysis, and a new set of parton distribution functions, ATLAS-epWZ16, is obtained. The ratio of strange-to-light sea-quark densities in the proton is determined more accurately than in previous determinations based on collider data only, and is established to be close to unity in the sensitivity range of the data. A new measurement of the CKM matrix element | V c s | is also provided.

NLO+NLL squark and gluino production cross sections with threshold-improved parton distributions

We present updated predictions for the cross sections for pair production of squarks and gluinos at the LHC Run II. First of all, we update the calculations based on NLO+NLL partonic cross sections by using the NNPDF3.0NLO global analysis. This study includes a full characterization of theoretical uncertainties from higher orders, PDFs and the strong coupling. Then we explore the implications for this calculation of the recent NNPDF3.0 PDFs with NLO+NLL threshold resummation. We find that the shift in the results induced by the threshold-improved PDFs is within the total theory uncertainty band of the calculation based on NLO PDFs. However, we also observe that the central values of the NLO+NLL cross sections are modified both in a qualitative and a quantitative way, illustrating the relevance and impact of using threshold-improved PDFs together with resummed partonic cross sections. The updated NLO+NLL cross sections based on NNPDF3.0NLO are publicly available in the NLL-fast format, and should be an important ingredient for the interpretation of the searches for supersymmetric particles at Run II.