The first collider search for dark matter arising from a strongly coupled hidden sector is presented and uses a data sample corresponding to 138 fb−1, collected with the CMS detector at the CERN LHC, at $$ \sqrt{s} $$ s = 13 TeV. The hidden sector is hypothesized to couple to the standard model (SM) via a heavy leptophobic Z′ mediator produced as a resonance in proton-proton collisions. The mediator decay results in two “semivisible” jets, containing both visible matter and invisible dark matter. The final state therefore includes moderate missing energy aligned with one of the jets, a signature ignored by most dark matter searches. No structure in the dijet transverse mass spectra compatible with the signal is observed. Assuming the Z′ boson has a universal coupling of 0.25 to the SM quarks, an inclusive search, relevant to any model that exhibits this kinematic behavior, excludes mediator masses of 1.5–4.0 TeV at 95% confidence level, depending on the other signal model parameters. To enhance the sensitivity of the search for this particular class of hidden sector models, a boosted decision tree (BDT) is trained using jet substructure variables to distinguish between semivisible jets and SM jets from background processes. When the BDT is employed to identify each jet in the dijet system as semivisible, the mediator mass exclusion increases to 5.1 TeV, for wider ranges of the other signal model parameters. These limits exclude a wide range of strongly coupled hidden sector models for the first time.

Two term neonates born within four days of each other at a small hospital developed sepsis and meningitis caused by a unique strain of Citrobacter diversus not previously reported to cause meningitis. Eleven (27.5%) of 40 other infants admitted to the nursery during the epidemic period developed rectal or umbilical colonization by C. diversus. Contact soon after birth with either of two nurses was more common among infected or colonized infants than among infants who were not infected or colonized. Hand cultures of both nurses and a rectal culture of one of the nurses yielded the epidemic strain. C. diversus may have been introduced into the nursery by the rectal carrier and spread person to person. Six weeks later continued surveillance identified a second cluster (of four colonized infants) associated with a mother who was a carrier of C. diversus and whose newborn infant became colonized at birth. The outbreak ended after strict control measures were used.

A search for heavy neutral leptons (HNLs), the right-handed Dirac or Majorana neutrinos, is performed in final states with three charged leptons (electrons or muons) using proton-proton collision data collected by the CMS experiment at $$ \sqrt{s} $$ s = 13 TeV at the CERN LHC. The data correspond to an integrated luminosity of 138 fb−1. The HNLs could be produced through mixing with standard model neutrinos ν. For small values of the HNL mass (<20 GeV) and the square of the HNL-ν mixing parameter (10−7–10−2), the decay length of these particles can be large enough so that the secondary vertex of the HNL decay can be resolved with the CMS silicon tracker. The selected final state consists of one lepton emerging from the primary proton-proton collision vertex, and two leptons forming a displaced, secondary vertex. No significant deviations from the standard model expectations are observed, and constraints are obtained on the HNL mass and coupling strength parameters, excluding previously unexplored regions of parameter space in the mass range 1–20 GeV and squared mixing parameter values as low as 10−7.

In the summer of 1981, an outbreak of diarrhea occurred in students and staff at a school for mentally retarded adults and children in Columbia, Missouri. Forty-one (48%) of 86 students and 38 (28%) of 137 staff members in the two dormitories with the lowest functioning students were ill. Enteroinvasive Escherichia coli 0124:H30 was isolated from 20 persons including six staff members, 13 students, and the ill mother of one of the students. Contact with students was associated with illness. Thirty-eight (33%) of the 115 student-care staff members and none of the 22 nonstudent-care staff members who worked in the two dormitories were ill (p = 0.004, chi-square). In the dormitory with the most dependent students, illness in student-care staff was associated with the number of contacts with ill students and with having taken a student home during the outbreak. Control measures to interrupt transmission included separation of symptomatic or culture-positive students from those who were well, and emphasizing handwashing. The authors present these findings as the first report of person-to-person transmission in an outbreak of enteroinvasive E. coli.

A measurement of the forward-backward asymmetry of pairs of oppositely charged leptons (dimuons and dielectrons) produced by the Drell-Yan process in proton-proton collisions is presented. The data sample corresponds to an integrated luminosity of 138 fb−1 collected with the CMS detector at the LHC at a center-of-mass energy of 13 TeV. The asymmetry is measured as a function of lepton pair mass for masses larger than 170 GeV and compared with standard model predictions. An inclusive measurement across both channels and the full mass range yields an asymmetry of 0.612 ± 0.005 (stat) ± 0.007 (syst). As a test of lepton flavor universality, the difference between the dimuon and dielectron asymmetries is measured as well. No statistically significant deviations from standard model predictions are observed. The measurements are used to set limits on the presence of additional gauge bosons. For a Z′ boson in the sequential standard model the observed (expected) 95% confidence level lower limit on the Z′ mass is 4.4 TeV (3.7 TeV).