The CP nature of the Higgs coupling to top quarks is addressed in this paper, in single charged lepton final states of tt¯h events produced in proton-proton collisions at the LHC. Pure scalar (h=H) ...and pseudoscalar (h=A) Higgs boson signal events, generated with MadGraph5_aMC@NLO, are fully reconstructed using a kinematic fit. Angular distributions of the decay products, as well as CP-sensitive asymmetries, are exploited to separate and gain sensitivity to possible pseudoscalar components of the Higgs boson and reduce the contribution from the dominant irreducible background tt¯bb¯. Significant differences are found between the pure CP-even and -odd signal hypotheses as well as with respect to the Standard Model background, in particular the tt¯bb¯ contribution. Such differences survive the event reconstruction, allowing one to define optimal observables to extract the Higgs couplings parameters from a global fit. A dedicated analysis is applied to efficiently identify signal events and reject as much as possible the expected Standard Model background. The results obtained are compared with a similar analysis in the dilepton channel. We show that the single lepton channel is more promising overall and can be used in combination to study the CP nature of the Higgs coupling to top quarks.
The DO collaboration is completing production of a 793 000 channel silicon strip tracking system for the DO upgrade. The tracker consists of 768 ladder and wedge assemblies including both single- and ...double-sided detectors. The production process includes burn-in of electronics, mechanical assembly under coordinate measuring machines, wire bonding, repair of bad channels, detector burn-in, laser testing, and final assembly. We describe observed failure modes of the detectors, including microdischarge and lithography defects. We present results of the production and testing process and describe the anticipated performance of the detector. Lessons for future production of large-scale tracking systems are discussed.
Evidence for a B-s(0)pi(+/-) State Askew, A.; Aushev, V.; Avila, C. ...
Physical review letters,
07/2016, Volume:
117, Issue:
2
Journal Article
Peer reviewed
Open access
We report evidence for a narrow structure, X(5568), in the decay sequence X(5568) -> B-s(0)pi(+/-), B-s(0) -> J/psi phi, J/psi -> mu(+)mu(-), phi -> K+K-. This is evidence for the first ...instance of a hadronic state with valence quarks of four different flavors. The mass and natural width of this state are measured to be m = 5567.8 +/- 2.9(stat)(-1.9)(+0.9) (syst) MeV/c(2) and Gamma = 21.9 +/- 6.4(stat)(-2.5)(+5.0) (syst) MeV/c(2). If the decay is X(5568) -> B-s*pi(+/-). B-s(0)gamma pi(+/-) with an unseen gamma, m(X(5568)) will be shifted up by m(B-s*) - m(B-s(0)) similar to 49 MeV/c(2). This measurement is based on 10.4 fb(-1) of p (p) over bar collision data at root s = 1.96 TeV collected by the D0 experiment at the Fermilab Tevatron collider.
We present evidence for the exotic charged charmoniumlike state Zc±(3900) decaying to J/ψπ± in semi-inclusive weak decays of b-flavored hadrons. The signal is correlated with a parent J/ψπ+π− system ...in the invariant-mass range 4.2–4.7 GeV that would include the exotic structure Y(4260). The study is based on 10.4 fb−1 of pp¯ collision data collected by the D0 experiment at the Fermilab Tevatron collider.
PDF
