P03.05.A Radiation-induced leukoencephalopathy (RIL) in glioma: unique injury dynamics following proton vs photon beam radiotherapy

Background

White matter injury after brain-directed radiotherapy (RT), aka radiation-induced leukoencephalopathy (RIL), is common in brain tumor patients. Differentiation from progressive disease can be challenging. Dosimetric advantages of protons (PRT) over photons (XRT) minimize radiation to healthy brain tissue, potentially limiting radiotoxic sequelae including RIL. We characterized RIL during periods of progression-free survival (PFS) in glioma patients irradiated with either PRT or XRT, hypothesizing that PRT would result in reduced RIL outside of the target field.

Material and Methods

34 patients (19 male; mean age = 40.10y) with grade 2/3 gliomas and a history of partial cranial RT were stratified by RT modality [XRT (n=17) vs PRT (n=17)] and matched on 11 criteria [age, sex, tumor type/location/laterality, mutational status (IDH; 1p19q deletion), concurrent/adjuvant chemotherapy, radiation dose/fractions] for retrospective analysis. RIL development was characterized longitudinally for up to 3 years post-RT via analysis of serial MRI T2/FLAIR sequences. A novel RIL scoring system with embedded Fazekas scale was designed to quantify injury severity at both global (whole brain) and hemispheric levels.

Results

Matched groups did not differ significantly on any demographic or clinical characteristics. Median PFS post-RT was 4.7 (XRT) and 5.1 (PRT) years. The novel RIL scoring system was reliable (intraclass correlation coefficient >0.9). There was a significant increase in global RIL in both XRT [F(3, 57)=8.63, p< .001] and PRT [F(3, 61)=4.69, p< .005] groups over time, relative to baseline (1-month post-RT). A majority [62% (XRT) and 72% (PRT)] developed moderate or severe RIL within 3 years, with the ipsilesional hemisphere more severely affected. Analysis of RIL injury dynamics (i.e., average % change between 1 and 3 years post-RT) at hemispheric level identified radiation modality-specific differences: XRT resulted in greater contralesional hemispheric injury than PRT [F(1, 31)=4.32, p<.05]. This effect was not observed in ipsilesional hemispheres.

Conclusion

RIL is common in glioma patients and quantifiable by characteristic imaging features, including early onset post-RT, greater ipsilesional injury burden, and progression over time. RIL injury dynamics appear to be radiation modality-specific, whereby XRT causes greater delayed injury in the remote, contralesional hemisphere. These findings may reflect dosimetric differences between protons and photons. The impact of such sequelae on cognitive function is subject of current investigation.

Relationships among owner consideration of euthanasia, caregiver burden, and treatment satisfaction in canine osteoarthritis

Although diagnosis of osteoarthritis (OA) has been recently linked to euthanasia in dogs, no prior work has examined the roles of caregiver burden or treatment satisfaction in this relationship. We expected that there would be an indirect effect of caregiver burden on the association between consideration of euthanasia and clinical signs of OA, but that this effect would be influenced by owner satisfaction. Cross-sectional online evaluations were completed by 277 owners of dogs with OA recruited through social media. Canine OA-related pain and functional impairment, owner consideration of euthanasia, caregiver burden, and satisfaction were examined. Relationships among OA-related pain and functional impairment, owner consideration of euthanasia, caregiver burden, and satisfaction were statistically significant (P 0.01 for all). Cross-sectional mediation analysis demonstrated a statistically significant indirect effect of caregiver burden on the relationship between consideration of euthanasia and OA-related clinical signs (bias-corrected 95% confidence interval [BC 95% CI], 0.001-0.009), which was significantly moderated by owner satisfaction (BC 95% CI, -0.003 to -0.0002). Findings align with prior work connecting canine OA to euthanasia. The current study extends past research to demonstrate that caregiver burden in the owner may be partially responsible for this relationship. The moderating role of owner satisfaction suggests that optimizing owner impressions of treatment and the veterinary team could attenuate these relationships, potentially decreasing the likelihood of premature euthanasia for dogs with OA.

Evaluation of prognostic risk models for postoperative pulmonary complications in adult patients undergoing major abdominal surgery: a systematic review and international external validation cohort study

BACKGROUND

Stratifying risk of postoperative pulmonary complications after major abdominal surgery allows clinicians to modify risk through targeted interventions and enhanced monitoring. In this study, we aimed to identify and validate prognostic models against a new consensus definition of postoperative pulmonary complications.

METHODS

We did a systematic review and international external validation cohort study. The systematic review was done in accordance with the Preferred Reporting Items for Systematic Reviews and Meta-Analyses guidelines. We searched MEDLINE and Embase on March 1, 2020, for articles published in English that reported on risk prediction models for postoperative pulmonary complications following abdominal surgery. External validation of existing models was done within a prospective international cohort study of adult patients (≥18 years) undergoing major abdominal surgery. Data were collected between Jan 1, 2019, and April 30, 2019, in the UK, Ireland, and Australia. Discriminative ability and prognostic accuracy summary statistics were compared between models for the 30-day postoperative pulmonary complication rate as defined by the Standardised Endpoints in Perioperative Medicine Core Outcome Measures in Perioperative and Anaesthetic Care (StEP-COMPAC). Model performance was compared using the area under the receiver operating characteristic curve (AUROCC).

FINDINGS

In total, we identified 2903 records from our literature search; of which, 2514 (86·6%) unique records were screened, 121 (4·8%) of 2514 full texts were assessed for eligibility, and 29 unique prognostic models were identified. Nine (31·0%) of 29 models had score development reported only, 19 (65·5%) had undergone internal validation, and only four (13·8%) had been externally validated. Data to validate six eligible models were collected in the international external validation cohort study. Data from 11 591 patients were available, with an overall postoperative pulmonary complication rate of 7·8% (n=903). None of the six models showed good discrimination (defined as AUROCC ≥0·70) for identifying postoperative pulmonary complications, with the Assess Respiratory Risk in Surgical Patients in Catalonia score showing the best discrimination (AUROCC 0·700 [95% CI 0·683-0·717]).

INTERPRETATION

In the pre-COVID-19 pandemic data, variability in the risk of pulmonary complications (StEP-COMPAC definition) following major abdominal surgery was poorly described by existing prognostication tools. To improve surgical safety during the COVID-19 pandemic recovery and beyond, novel risk stratification tools are required.

FUNDING

British Journal of Surgery Society.

Reduction in shock burden with catheter ablation versus escalated antiarrhythmic drug therapy: Insights from the VANISH trial

Funding Acknowledgements

Type of funding sources: Public grant(s) – National budget only. Main funding source(s): 1. Canadian Institutes of Health Research (CIHR)

2. Additional financial support from St. Jude Medical and Biosense Webster

Background

Recurrent shocks for ventricular tachycardia (VT) are associated with an increased risk of heart failure and mortality and have a negative influence on quality of life. Catheter ablation has been shown to improve VT event-free survival in patients with antiarrhythmic drug (AAD)-refractory VT and prior myocardial infarction (MI); however, the effects of ablation on shock burden has yet to be investigated.

Purpose

Our primary objectives were to compare the shock-treated VT event burden and appropriate shock burden following randomization to treatment with either catheter ablation or escalated AAD therapy among VT patients with prior MI in the Ventricular tachycardia AblatioN versus escalated antiarrhythmic drug therapy in Ischemic Heart disease (VANISH) randomized trial.

Methods

Recurrent event analyses were performed using the intention-to-treat population of the VANISH trial. Shock-treated VT event burden was defined as the total number of VT events treated with ≥1 appropriate internal or external shocks. Appropriate shock burden was defined as the total number of appropriate internal and external shocks delivered, regardless of the number of VT events. All VT events and implantable cardioverter defibrillator (ICD) therapies were adjudicated by reviewers blinded to the treatment allocation. Three recurrent event models were used to compare the shock burden between treatment arms (Anderson-Gill (AG), Frailty, and Prentice, Williams, and Peterson Total Time (PWP-TT). Each model clustered by patient and accounted for competing risk of death with the Fine and Gray sub-distributions hazards model.

Results

Of the 259 patients enrolled in the VANISH trial [median age 69.8 (IQR 63.0-74.2) years, 7.0% women], 132 patients were randomized to ablation and 129 patients to escalated AAD therapy. Over a median follow-up of 23.4 (IQR 14.7-40.4) months, there were 138 shock-treated VT events [39.07 (95% CI 33.14-46.07) shock-treated VT events per 100 person-years] in the ablation arm and 218 shock-treated VT events [64.60 (95% CI 56.49–73.84) shock-treated VT events per 100 person-years] in the escalated AAD therapy arm (Figure 1). Ablation patients had a 40% lower shock-treated VT event burden (ie. number of shock-treated VT events) compared to patients randomized to escalated AAD therapy [Figure 1; AG HR 0.60 (95% 0.38-0.95)]. Further, there was also a statistically significant reduction in the appropriate shock burden (i.e. number of appropriate shocks) among ablation patients (169 appropriate shocks) compared to escalated AAD therapy patients (266 appropriate shocks) [Figure 1; AG HR 0.61 (95% CI 0.37-0.96)]. All results were consistent between the 3 recurrent event models.

Conclusion

Among patients with AAD-refractory VT and a prior MI, catheter ablation reduced shock-treated VT event burden and appropriate shock burden compared to escalated AAD therapy.

Comparing steam-flaked and pelleted barley grain in a feed-first guided-flow automated milking system for Holstein cows

Provision of a palatable feed in automated milking systems (AMS) is considered an essential motivating factor to encourage voluntary visits to the milking stall. Although the quantity and composition of AMS concentrates have been previously investigated, the form of the concentrate has not been extensively evaluated. The objective of this study was to evaluate the effects of feeding pelleted (PB; 132.9 ± 56 DIM, 47.4 ± 9.51 kg/d milk yield) versus steam-flaked barley (SFB; 133.0 ± 63 DIM, 40.5 ± 8.23 kg/d milk yield) in an AMS on dry matter intake, AMS visits, milk and milk component yield, and partial mixed ration (PMR) feeding behavior. Twenty-nine Holstein cows of varying parities were enrolled in this study. Cows were housed in freestall housing with a feed-first guided-flow barn design; 7 cows were housed in a separate freestall pen to enable individual PMR intake and feeding behavior monitoring. This study was conducted as a 2-way crossover, with two 21-d periods in which each cow received the same basal PMR but was offered 2 kg/d (dry matter basis) of PB or SFB in the AMS. Cows receiving the SFB had fewer voluntary AMS visits (2.71 vs. 2.90 ± 0.051, no./d), tended to have a longer interval between milkings (541.7 vs. 505.8 ± 21.02 min), spent more time in the holding pen before entering the AMS (139.9 vs. 81.2 ± 11.68 min/d), and had lower total box time (19.7 vs. 21.4 ± 0.35 min/d) than cows fed PB. Despite changes in AMS attendance, there were no differences for average milk (44.0 kg/d), fat (1.62 kg/d), and protein (1.47 kg/d) yields or AMS concentrate intake (2.02 kg/d). These behavioral changes indicate that offering SFB as an alternative to PB may reduce motivation for cows to voluntarily enter the AMS.

A Type 1 Diabetes Genetic Risk Score Predicts Progression of Islet Autoimmunity and Development of Type 1 Diabetes in Individuals at Risk

OBJECTIVE

We tested the ability of a type 1 diabetes (T1D) genetic risk score (GRS) to predict progression of islet autoimmunity and T1D in at-risk individuals.

RESEARCH DESIGN AND METHODS

We studied the 1,244 TrialNet Pathway to Prevention study participants (T1D patients' relatives without diabetes and with one or more positive autoantibodies) who were genotyped with Illumina ImmunoChip (median [range] age at initial autoantibody determination 11.1 years [1.2-51.8], 48% male, 80.5% non-Hispanic white, median follow-up 5.4 years). Of 291 participants with a single positive autoantibody at screening, 157 converted to multiple autoantibody positivity and 55 developed diabetes. Of 953 participants with multiple positive autoantibodies at screening, 419 developed diabetes. We calculated the T1D GRS from 30 T1D-associated single nucleotide polymorphisms. We used multivariable Cox regression models, time-dependent receiver operating characteristic curves, and area under the curve (AUC) measures to evaluate prognostic utility of T1D GRS, age, sex, Diabetes Prevention Trial-Type 1 (DPT-1) Risk Score, positive autoantibody number or type, HLA DR3/DR4-DQ8 status, and race/ethnicity. We used recursive partitioning analyses to identify cut points in continuous variables.

RESULTS

Higher T1D GRS significantly increased the rate of progression to T1D adjusting for DPT-1 Risk Score, age, number of positive autoantibodies, sex, and ethnicity (hazard ratio [HR] 1.29 for a 0.05 increase, 95% CI 1.06-1.6; P = 0.011). Progression to T1D was best predicted by a combined model with GRS, number of positive autoantibodies, DPT-1 Risk Score, and age (7-year time-integrated AUC = 0.79, 5-year AUC = 0.73). Higher GRS was significantly associated with increased progression rate from single to multiple positive autoantibodies after adjusting for age, autoantibody type, ethnicity, and sex (HR 2.27 for GRS >0.295, 95% CI 1.47-3.51; P = 0.0002).

CONCLUSIONS

The T1D GRS independently predicts progression to T1D and improves prediction along T1D stages in autoantibody-positive relatives.

Measurement of b hadron lifetimes in pp collisions at s = 8 TeV

Measurements are presented of the lifetimes of theB 0 ,B s 0 , Λ b 0 , and B c + hadrons using the decay channelsB 0 → J / ψ K ∗ ( 892 ) 0 ,B 0 → J / ψ K S 0 ,B s 0 → J / ψ π + π - ,B s 0 → J / ψ ϕ ( 1020 ) ,Λ b 0 → J / ψ Λ 0 , andB c + → J / ψ π + . The data sample, corresponding to an integrated luminosity of 19.7fb -1 , was collected by the CMS detector at the LHC in proton-proton collisions ats = 8 TeV . TheB 0 lifetime is measured to be 453.0 ± 1.6 (stat) ± 1.8 (syst) μ m in J / ψ K ∗ ( 892 ) 0 and 457.8 ± 2.7 (stat) ± 2.8 (syst) μ m in J / ψ K S 0 , which results in a combined measurement of c τ B 0 = 454.1 ± 1.4 (stat) ± 1.7 (syst) μ m . The effective lifetime of theB s 0 meson is measured in two decay modes, with contributions from different amounts of the heavy and light eigenstates. This results in two different measured lifetimes: c τ B s 0 → J / ψ π + π - = 502.7 ± 10.2 (stat) ± 3.4 (syst) μ m and c τ B s 0 → J / ψ ϕ ( 1020 ) = 443.9 ± 2.0 (stat) ± 1.5 (syst) μ m . The Λ b 0 lifetime is found to be 442.9 ± 8.2 (stat) ± 2.8 (syst) μ m . The precision from each of these channels is as good as or better than previous measurements. The B c + lifetime, measured with respect to theB + to reduce the systematic uncertainty, is 162.3 ± 7.8 (stat) ± 4.2 (syst) ± 0.1 ( τ B + ) μ m . All results are in agreement with current world-average values.

Measurement of Prompt D^{0} Meson Azimuthal Anisotropy in Pb-Pb Collisions at sqrt[s_{NN}]=5.02 TeV

The prompt D^{0} meson azimuthal anisotropy coefficients, v_{2} and v_{3}, are measured at midrapidity (|y|<1.0) in Pb-Pb collisions at a center-of-mass energy sqrt[s_{NN}]=5.02  TeV per nucleon pair with data collected by the CMS experiment. The measurement is performed in the transverse momentum (p_{T}) range of 1 to 40  GeV/c, for central and midcentral collisions. The v_{2} coefficient is found to be positive throughout the p_{T} range studied. The first measurement of the prompt D^{0} meson v_{3} coefficient is performed, and values up to 0.07 are observed for p_{T} around 4  GeV/c. Compared to measurements of charged particles, a similar p_{T} dependence, but smaller magnitude for p_{T}<6  GeV/c, is found for prompt D^{0} meson v_{2} and v_{3} coefficients. The results are consistent with the presence of collective motion of charm quarks at low p_{T} and a path length dependence of charm quark energy loss at high p_{T}, thereby providing new constraints on the theoretical description of the interactions between charm quarks and the quark-gluon plasma.

Measurement of associated Z + charm production in proton-proton collisions at s = 8 TeV

A study of the associated production of a Z boson and a charm quark jet ( Z + c ), and a comparison to production with a b quark jet ( Z + b ), in p p collisions at a centre-of-mass energy of 8TeV are presented. The analysis uses a data sample corresponding to an integrated luminosity of 19.7fb - 1 , collected with the CMS detector at the CERN LHC. The Z boson candidates are identified through their decays into pairs of electrons or muons. Jets originating from heavy flavour quarks are identified using semileptonic decays of c or b flavoured hadrons and hadronic decays of charm hadrons. The measurements are performed in the kinematic region with two leptons withp T ℓ > 20 GeV ,| η ℓ | < 2.1 , 71 < m ℓ ℓ < 111 GeV , and heavy flavour jets withp T jet > 25 GeV and| η jet | < 2.5 . The Z + c production cross section is measured to be σ ( p p → Z + c + X ) B ( Z → ℓ + ℓ - ) = 8.8 ± 0.5 (stat) ± 0.6 (syst) pb . The ratio of the Z + c and Z + b production cross sections is measured to be σ ( p p → Z + c + X ) / σ ( p p → Z + b + X ) = 2.0 ± 0.2 (stat) ± 0.2 (syst) . The Z + c production cross section and the cross section ratio are also measured as a function of the transverse momentum of the Z boson and of the heavy flavour jet. The measurements are compared with theoretical predictions.

Measurement of the Splitting Function in pp and Pb-Pb Collisions at sqrt[s_{NN}]=5.02 TeV

Data from heavy ion collisions suggest that the evolution of a parton shower is modified by interactions with the color charges in the dense partonic medium created in these collisions, but it is not known where in the shower evolution the modifications occur. The momentum ratio of the two leading partons, resolved as subjets, provides information about the parton shower evolution. This substructure observable, known as the splitting function, reflects the process of a parton splitting into two other partons and has been measured for jets with transverse momentum between 140 and 500 GeV, in pp and PbPb collisions at a center-of-mass energy of 5.02 TeV per nucleon pair. In central PbPb collisions, the splitting function indicates a more unbalanced momentum ratio, compared to peripheral PbPb and pp collisions.. The measurements are compared to various predictions from event generators and analytical calculations.

Suppression of Excited ϒ States Relative to the Ground State in Pb-Pb Collisions at sqrt[s]_{NN}=5.02 TeV

The relative yields of ϒ mesons produced in pp and Pb-Pb collisions at sqrt[s_{NN}]=5.02  TeV and reconstructed via the dimuon decay channel are measured using data collected by the CMS experiment. Double ratios are formed by comparing the yields of the excited states, ϒ(2S) and ϒ(3S), to the ground state, ϒ(1S), in both Pb-Pb and pp collisions at the same center-of-mass energy. The double ratios, [ϒ(nS)/ϒ(1S)]_{Pb-Pb}/[ϒ(nS)/ϒ(1S)]_{pp}, are measured to be 0.308±0.055(stat)±0.019(syst) for the ϒ(2S) and less than 0.26 at 95% confidence level for the ϒ(3S). No significant ϒ(3S) signal is found in the Pb-Pb data. The double ratios are studied as a function of collision centrality, as well as ϒ transverse momentum and rapidity. No significant dependencies are observed.

Study of dijet events with a large rapidity gap between the two leading jets in pp collisions at s = 7 TeV

Events with no charged particles produced between the two leading jets are studied in proton-proton collisions ats = 7 TeV . The jets were required to have transverse momentump T jet > 40 GeV and pseudorapidity1.5 < | η jet | < 4.7 , and to have values of η jet with opposite signs. The data used for this study were collected with the CMS detector during low-luminosity running at the LHC, and correspond to an integrated luminosity of 8pb - 1 . Events with no charged particles withp T > 0.2 GeV in the interval - 1 < η < 1 between the jets are observed in excess of calculations that assume no color-singlet exchange. The fraction of events with such a rapidity gap, amounting to 0.5-1% of the selected dijet sample, is measured as a function of the p T of the second-leading jet and of the rapidity separation between the jets. The data are compared to previous measurements at the Tevatron, and to perturbative quantum chromodynamics calculations based on the Balitsky-Fadin-Kuraev-Lipatov evolution equations, including different models of the non-perturbative gap survival probability.

Observation of Correlated Azimuthal Anisotropy Fourier Harmonics in pp and p+Pb Collisions at the LHC

The azimuthal anisotropy Fourier coefficients (v_{n}) in 8.16 TeV p+Pb data are extracted via long-range two-particle correlations as a function of the event multiplicity and compared to corresponding results in pp and PbPb collisions. Using a four-particle cumulant technique, v_{n} correlations are measured for the first time in pp and p+Pb collisions. The v_{2} and v_{4} coefficients are found to be positively correlated in all collision systems. For high-multiplicity p+Pb collisions, an anticorrelation of v_{2} and v_{3} is observed, with a similar correlation strength as in PbPb data at the same multiplicity. The new correlation results strengthen the case for a common origin of the collectivity seen in p+Pb and PbPb collisions in the measured multiplicity range.

Measurements of the p p → Z Z production cross section and the Z → 4 ℓ branching fraction, and constraints on anomalous triple gauge couplings at s = 13 TeV

Four-lepton production in proton-proton collisions, p p → ( Z / γ ∗ ) ( Z / γ ∗ ) → 4 ℓ , where ℓ = e or μ , is studied at a center-of-mass energy of 13TeV with the CMS detector at the LHC. The data sample corresponds to an integrated luminosity of 35.9fb - 1 . The ZZ production cross section, σ ( p p → Z Z ) = 17.2 ± 0.5 (stat) ± 0.7 (syst) ± 0.4 (theo) ± 0.4 (lumi) pb , measured using events with two opposite-sign, same-flavor lepton pairs produced in the mass region 60 < m ℓ + ℓ - < 120 GeV , is consistent with standard model predictions. Differential cross sections are measured and are well described by the theoretical predictions. The Z boson branching fraction to four leptons is measured to be B ( Z → 4 ℓ ) = 4 . 83 - 0.22 + 0.23 ( s t a t ) - 0.29 + 0.32 ( s y s t ) ± 0.08 ( t h e o ) ± 0.12 ( l u m i ) × 10 - 6 for events with a four-lepton invariant mass in the range 80 < m 4 ℓ < 100 GeV and a dilepton massm ℓ ℓ > 4 GeV for all opposite-sign, same-flavor lepton pairs. The results agree with standard model predictions. The invariant mass distribution of the four-lepton system is used to set limits on anomalous ZZZ and ZZ γ couplings at 95% confidence level: - 0.0012 < f 4 Z < 0.0010 , - 0.0010 < f 5 Z < 0.0013 , - 0.0012 < f 4 γ < 0.0013 , - 0.0012 < f 5 γ < 0.0013 .

Measurements of the p p → Z Z production cross section and the Z → 4 ℓ branching fraction, and constraints on anomalous triple gauge couplings at s = 13 TeV

Four-lepton production in proton-proton collisions, p p → ( Z / γ ∗ ) ( Z / γ ∗ ) → 4 ℓ , where ℓ = e or μ , is studied at a center-of-mass energy of 13 TeV with the CMS detector at the LHC. The data sample corresponds to an integrated luminosity of 35.9 fb - 1 . The ZZ production cross section, σ ( p p → Z Z ) = 17.2 ± 0.5 (stat) ± 0.7 (syst) ± 0.4 (theo) ± 0.4 (lumi) pb , measured using events with two opposite-sign, same-flavor lepton pairs produced in the mass region 60 < m ℓ + ℓ - < 120 GeV , is consistent with standard model predictions. Differential cross sections are measured and are well described by the theoretical predictions. The Z boson branching fraction to four leptons is measured to be B ( Z → 4 ℓ ) = 4 . 83 - 0.22 + 0.23 ( s t a t ) - 0.29 + 0.32 ( s y s t ) ± 0.08 ( t h e o ) ± 0.12 ( l u m i ) × 10 - 6 for events with a four-lepton invariant mass in the range 80 < m 4 ℓ < 100 GeV and a dilepton mass m ℓ ℓ > 4 GeV for all opposite-sign, same-flavor lepton pairs. The results agree with standard model predictions. The invariant mass distribution of the four-lepton system is used to set limits on anomalous ZZZ and ZZ γ couplings at 95% confidence level: - 0.0012 < f 4 Z < 0.0010 , - 0.0010 < f 5 Z < 0.0013 , - 0.0012 < f 4 γ < 0.0013 , - 0.0012 < f 5 γ < 0.0013 .

Search for dark matter produced in association with heavy-flavor quark pairs in proton-proton collisions at s = 13 TeV

A search is presented for an excess of events with heavy-flavor quark pairs ( t t ¯ and b b ¯ ) and a large imbalance in transverse momentum in data from proton-proton collisions at a center-of-mass energy of 13TeV . The data correspond to an integrated luminosity of 2.2fb - 1 collected with the CMS detector at the CERN LHC. No deviations are observed with respect to standard model predictions. The results are used in the first interpretation of dark matter production in t t ¯ and b b ¯ final states in a simplified model. This analysis is also the first to perform a statistical combination of searches for dark matter produced with different heavy-flavor final states. The combination provides exclusions that are stronger than those achieved with individual heavy-flavor final states.

Search for Evidence of the Type-III Seesaw Mechanism in Multilepton Final States in Proton-Proton Collisions at sqrt[s]=13 TeV

A search for a signal consistent with the type-III seesaw mechanism in events with three or more electrons or muons is presented. The data sample consists of proton-proton collisions at sqrt[s]=13  TeV collected by the CMS experiment at the LHC in 2016 and corresponds to an integrated luminosity of 35.9  fb^{-1}. Selection criteria based on the number of leptons and the invariant mass of oppositely charged lepton pairs are used to distinguish the signal from the standard model background. The observations are consistent with the expectations from standard model processes. The results are used to place limits on the production of heavy fermions of the type-III seesaw model as a function of the branching ratio to each lepton flavor. In the scenario of equal branching fractions to each lepton flavor, heavy fermions with masses below 840 GeV are excluded. This is the most sensitive probe to date of the type-III seesaw mechanism.

Measurements of the associated production of a Z boson and b jets in pp collisions at s = 8 TeV

Measurements of the associated production of a Z boson with at least one jet originating from a b quark in proton-proton collisions ats = 8 TeV are presented. Differential cross sections are measured with data collected by the CMS experiment corresponding to an integrated luminosity of 19.8fb - 1 . Z bosons are reconstructed through their decays to electrons and muons. Cross sections are measured as a function of observables characterizing the kinematics of the b jet and the Z boson. Ratios of differential cross sections for the associated production with at least one b jet to the associated production with any jet are also presented. The production of a Z boson with at least two b jets is investigated, and differential cross sections are measured for the dijet system. Results are compared to theoretical predictions, testing two different flavour schemes for the choice of initial-state partons.

Measurement of the triple-differential dijet cross section in proton-proton collisions at s = 8 TeV and constraints on parton distribution functions

A measurement is presented of the triple-differential dijet cross section at a centre-of-mass energy of 8TeV using 19.7fb -1 of data collected with the CMS detector in proton-proton collisions at the LHC. The cross section is measured as a function of the average transverse momentum, half the rapidity separation, and the boost of the two leading jets in the event. The cross section is corrected for detector effects and compared to calculations in perturbative quantum chromodynamics at next-to-leading order accuracy, complemented with electroweak and nonperturbative corrections. New constraints on parton distribution functions are obtained and the inferred value of the strong coupling constant isα S ( M Z ) = 0.1199 ± 0.0015 ( exp ) - 0.0020 + 0.0031 ( theo ) , where M Z is the mass of the Z boson.

Search for new phenomena with the M T 2 variable in the all-hadronic final state produced in proton-proton collisions at s = 13 TeV

A search for new phenomena is performed using events with jets and significant transverse momentum imbalance, as inferred through the M T 2 variable. The results are based on a sample of proton-proton collisions collected in 2016 at a center-of-mass energy of 13TeV with the CMS detector and corresponding to an integrated luminosity of 35.9fb -1 . No excess event yield is observed above the predicted standard model background, and the results are interpreted as exclusion limits at 95% confidence level on the masses of predicted particles in a variety of simplified models of R-parity conserving supersymmetry. Depending on the details of the model, 95% confidence level lower limits on the gluino (light-flavor squark) masses are placed up to 2025 (1550)GeV . Mass limits as high as 1070 (1175)GeV are set on the masses of top (bottom) squarks. Information is provided to enable re-interpretation of these results, including model-independent limits on the number of non-standard model events for a set of simplified, inclusive search regions.

Measurement of the B^{±} Meson Nuclear Modification Factor in Pb-Pb Collisions at sqrt[s_{NN}]=5.02 TeV

The differential production cross sections of B^{±} mesons are measured via the exclusive decay channels B^{±}→J/ψK^{±}→μ^{+}μ^{-}K^{±} as a function of transverse momentum in pp and Pb-Pb collisions at a center-of-mass energy sqrt[s_{NN}]=5.02  TeV per nucleon pair with the CMS detector at the LHC. The pp(Pb-Pb) data set used for this analysis corresponds to an integrated luminosity of 28.0  pb^{-1} (351  μb^{-1}). The measurement is performed in the B^{±} meson transverse momentum range of 7 to 50  GeV/c, in the rapidity interval |y|<2.4. In this kinematic range, a strong suppression of the production cross section by about a factor of 2 is observed in the Pb-Pb system in comparison to the expectation from pp reference data. These results are found to be roughly compatible with theoretical calculations incorporating beauty quark diffusion and energy loss in a quark-gluon plasma.

Search for Supersymmetry in pp Collisions at sqrt[s]=13 TeV in the Single-Lepton Final State Using the Sum of Masses of Large-Radius Jets

Results are reported from a search for supersymmetric particles in proton-proton collisions in the final state with a single lepton, multiple jets, including at least one b-tagged jet, and large missing transverse momentum. The search uses a sample of proton-proton collision data at sqrt[s]=13  TeV recorded by the CMS experiment at the LHC, corresponding to an integrated luminosity of 35.9  fb^{-1}. The observed event yields in the signal regions are consistent with those expected from standard model backgrounds. The results are interpreted in the context of simplified models of supersymmetry involving gluino pair production, with gluino decay into either on- or off-mass-shell top squarks. Assuming that the top squarks decay into a top quark plus a stable, weakly interacting neutralino, scenarios with gluino masses up to about 1.9 TeV are excluded at 95% confidence level for neutralino masses up to about 1 TeV.

Search for Charged Higgs Bosons Produced via Vector Boson Fusion and Decaying into a Pair of W and Z Bosons Using pp Collisions at sqrt[s]=13 TeV

A search for charged Higgs bosons produced via vector boson fusion and decaying into W and Z bosons using proton-proton collisions at sqrt[s]=13  TeV is presented. The data sample corresponds to an integrated luminosity of 15.2  fb^{-1} collected with the CMS detector in 2015 and 2016. The event selection requires three leptons (electrons or muons), two jets with large pseudorapidity separation and high dijet mass, and missing transverse momentum. The observation agrees with the standard model prediction. Limits on the vector boson fusion production cross section times branching fraction for new charged physical states are reported as a function of mass from 200 to 2000 GeV and interpreted in the context of Higgs triplet models.

Search for heavy resonances that decay into a vector boson and a Higgs boson in hadronic final states at s = 13 TeV

A search for heavy resonances with masses above 1TeV , decaying to final states containing a vector boson and a Higgs boson, is presented. The search considers hadronic decays of the vector boson, and Higgs boson decays to b quarks. The decay products are highly boosted, and each collimated pair of quarks is reconstructed as a single, massive jet. The analysis is performed using a data sample collected in 2016 by the CMS experiment at the LHC in proton-proton collisions at a center-of-mass energy of 13TeV , corresponding to an integrated luminosity of 35.9fb - 1 . The data are consistent with the background expectation and are used to place limits on the parameters of a theoretical model with a heavy vector triplet. In the benchmark scenario with mass-degenerate W ' andZ ' bosons decaying predominantly to pairs of standard model bosons, for the first time heavy resonances for masses as high as 3.3TeV are excluded at 95% confidence level, setting the most stringent constraints to date on such states decaying into a vector boson and a Higgs boson.

Search for Low Mass Vector Resonances Decaying to Quark-Antiquark Pairs in Proton-Proton Collisions at sqrt[s]=13 TeV

A search is reported for a narrow vector resonance decaying to quark-antiquark pairs in proton-proton collisions at sqrt[s]=13  TeV, collected with the CMS detector at the LHC. The data sample corresponds to an integrated luminosity of 2.7   fb^{-1}. The vector resonance is produced at large transverse momenta, with its decay products merged into a single jet. The resulting signature is a peak over background in the distribution of the invariant mass of the jet. The results are interpreted in the framework of a leptophobic vector resonance and no evidence is found for such particles in the mass range of 100-300 GeV. Upper limits at 95% confidence level on the production cross section are presented in a region of mass-coupling phase space previously unexplored at the LHC. The region below 140 GeV has not been explored by any previous experiments.

Search for physics beyond the standard model in events with two leptons of same sign, missing transverse momentum, and jets in proton-proton collisions at s = 13 TeV

A data sample of events from proton-proton collisions with two isolated same-sign leptons, missing transverse momentum, and jets is studied in a search for signatures of new physics phenomena by the CMS Collaboration at the LHC. The data correspond to an integrated luminosity of 35.9fb - 1 , and a center-of-mass energy of 13TeV . The properties of the events are consistent with expectations from standard model processes, and no excess yield is observed. Exclusion limits at 95% confidence level are set on cross sections for the pair production of gluinos, squarks, and same-sign top quarks, as well as top-quark associated production of a heavy scalar or pseudoscalar boson decaying to top quarks, and on the standard model production of events with four top quarks. The observed lower mass limits are as high as 1500GeV for gluinos, 830GeV for bottom squarks. The excluded mass range for heavy (pseudo)scalar bosons is 350-360 (350-410)GeV . Additionally, model-independent limits in several topological regions are provided, allowing for further interpretations of the results.

Study of Jet Quenching with Z+jet Correlations in Pb-Pb and pp Collisions at sqrt[s]_{NN}=5.02 TeV

The production of jets in association with Z bosons, reconstructed via the μ^{+}μ^{-} and e^{+}e^{-} decay channels, is studied in pp and, for the first time, in Pb-Pb collisions. Both data samples were collected by the CMS experiment at the LHC, at a nucleon-nucleon center-of-mass energy of 5.02 TeV. The Pb-Pb collisions were analyzed in the 0%-30% centrality range. The back-to-back azimuthal alignment was studied in both pp and Pb-Pb collisions for Z bosons with transverse momentum p_{T}^{Z}>60  GeV/c and a recoiling jet with p_{T}^{jet}>30  GeV/c. The p_{T} imbalance x_{jZ}=p_{T}^{jet}/p_{T}^{Z}, as well as the average number of jet partners per Z, R_{jZ}, was studied in intervals of p_{T}^{Z}. The R_{jZ} is found to be smaller in Pb-Pb than in pp collisions, which suggests that in Pb-Pb collisions a larger fraction of partons associated with the Z bosons fall below the 30  GeV/c p_{T}^{jet} threshold because they lose energy.

Measurement of the jet mass in highly boosted [Formula: see text] events from pp collisions at [Formula: see text][Formula: see text]

The first measurement of the jet mass [Formula: see text] of top quark jets produced in [Formula: see text] events from pp collisions at [Formula: see text] [Formula: see text] is reported for the jet with the largest transverse momentum [Formula: see text] in highly boosted hadronic top quark decays. The data sample, collected with the CMS detector, corresponds to an integrated luminosity of 19.7[Formula: see text]. The measurement is performed in the lepton+jets channel in which the products of the semileptonic decay [Formula: see text] with [Formula: see text] where [Formula: see text] is an electron or muon, are used to select [Formula: see text] events with large Lorentz boosts. The products of the fully hadronic decay [Formula: see text] with [Formula: see text] are reconstructed using a single Cambridge-Aachen jet with distance parameter [Formula: see text], and [Formula: see text] [Formula: see text]. The [Formula: see text] cross section as a function of [Formula: see text] is unfolded at the particle level and is used to test the modelling of highly boosted top quark production. The peak position of the [Formula: see text] distribution is sensitive to the top quark mass [Formula: see text], and the data are used to extract a value of [Formula: see text] to assess this sensitivity.

Measurement of double-differential cross sections for top quark pair production in pp collisions at [Formula: see text][Formula: see text] and impact on parton distribution functions

Normalized double-differential cross sections for top quark pair ([Formula: see text]) production are measured in pp collisions at a centre-of-mass energy of 8[Formula: see text] with the CMS experiment at the LHC. The analyzed data correspond to an integrated luminosity of 19.7[Formula: see text]. The measurement is performed in the dilepton [Formula: see text] final state. The [Formula: see text] cross section is determined as a function of various pairs of observables characterizing the kinematics of the top quark and [Formula: see text] system. The data are compared to calculations using perturbative quantum chromodynamics at next-to-leading and approximate next-to-next-to-leading orders. They are also compared to predictions of Monte Carlo event generators that complement fixed-order computations with parton showers, hadronization, and multiple-parton interactions. Overall agreement is observed with the predictions, which is improved when the latest global sets of proton parton distribution functions are used. The inclusion of the measured [Formula: see text] cross sections in a fit of parametrized parton distribution functions is shown to have significant impact on the gluon distribution.