208869198
Measurement of angular correlations of jets at s=1.96 TeV and determination of the strong coupling at high momentum transfers
We present a measurement of the average value of a new observable at hadron colliders that is sensitive to QCD dynamics and to the strong coupling constant, while being only weakly sensitive to parton distribution functions. The observable measures the angular correlations of jets and is defined as the number of neighboring jets above a given transverse momentum threshold which accompany a given jet within a given distance Delta-R in the plane of rapidity and azimuthal angle. The ensemble average over all jets in an inclusive jet sample is measured and the results are presented as a function of transverse momentum of the inclusive jets, in different regions of Delta-R and for different transverse momentum requirements for the neighboring jets. The measurement is based on a data set corresponding to an integrated luminosity of 0.7 fb-1 collected with the D0 detector at the Fermilab Tevatron Collider in pp-bar collisions at sqrt(s)=1.96 The results are well described by a perturbative QCD calculation in next-to-leading order in the strong coupling constant, corrected for non-perturbative effects. From these results, we extract the strong coupling and test the QCD predictions for its running over a range of momentum transfers of 50-400 GeV.
11077644
Search for violation of Lorentz invariance in top quark pair production and decay.
Using data collected with the D0 detector at the Fermilab Tevatron Collider, corresponding to 5.3 fb(-1) of integrated luminosity, we search for violation of Lorentz invariance by examining the tt[over ¯] production cross section in lepton+jets final states. We quantify this violation using the standard-model extension framework, which predicts a dependence of the tt[over ¯] production cross section on sidereal time as the orientation of the detector changes with the rotation of the Earth. Within this framework, we measure components of the matrices (c(Q))(μν33) and (c(U))(μν33) containing coefficients used to parametrize violation of Lorentz invariance in the top quark sector. Within uncertainties, these coefficients are found to be consistent with zero.
56117570
A 3000 element lead-glass electromagnetic calorimeter
Abstract A 3045 element lead glass calorimeter and an associated fast trigger processor have been constructed, tested and implemented in BNL experiment E852 in conjunction with the multi-particle spectrometer (MPS). Approximately, 10 9 all-neutral and neutral plus charged triggers were recorded with this apparatus during data runs in 1994 and 1995. This paper reports on the construction, testing and performance of this lead glass calorimeter and the associated trigger processor.
14275742
Search for long-lived charged massive particles with the D0 detector.
We search for long-lived charged massive particles using 1.1 fb;{-1} of data collected by the D0 detector at the Fermilab Tevatron pp[over ] Collider. Time-of-flight information is used to search for pair produced long-lived tau sleptons, gauginolike charginos, and Higgsino-like charginos. We find no evidence of a signal and set 95% C.L. cross section upper limits for staus, which vary from 0.31 to 0.04 pb for stau masses between 60 and 300 GeV. We also set lower mass limits of 206 GeV (171 GeV) for pair produced charged gauginos (Higgsinos).
9414980
Combination of CDF and D0 measurements of the W boson helicity in top quark decays
We report the combination of recent measurements of the helicity of the W boson from top quark decay by the CDF and D0 collaborations, based on data samples corresponding to integrated luminosities of 2.7-5.4 fb(-1) of p (p) over bar collisions collected during Run II of the Fermilab Tevatron collider. Combining measurements that simultaneously determine the fractions of W bosons with longitudinal (f(0)) and right-handed (f(+)) helicities, we find f(0) = 0.722 +/- 0.081[+/- 0.062(stat) +/- 0.052(syst)] and f(+) = -0.033 +/- 0.046[+/- 0.034(stat) +/- 0.031(syst)]. Combining measurements where one of the helicity fractions is fixed to the value expected in the standard model, we find f(0) = 0.682 +/- 0.057[+/- 0.035(stat) +/- 0.046(syst)] for fixed f(+) and f(+) = -0.015 +/- 0.035[+/- 0.018(stat) +/- 0.030(syst)] for fixed f(0). The results are consistent with standard model expectations.
209839914
Higgs Boson Studies at the Tevatron
We combine searches by the CDF and D0 Collaborations for the standard model Higgs boson with mass in the range 90--200 GeV/c2 produced in the gluon-gluon fusion, WH, ZH, tt¯H, and vector boson fusion processes, and decaying in the H→bb¯, H→W+W−, H→ZZ, H→τ+τ−, and H→γγ modes. The data correspond to integrated luminosities of up to 10 fb−1 and were collected at the Fermilab Tevatron in pp¯ collisions at s√=1.96 TeV. The searches are also interpreted in the context of fermiophobic and fourth generation models. We observe a significant excess of events in the mass range between 115 and 140 GeV/c2. The local significance corresponds to 3.0 standard deviations at mH=125 GeV/c2, consistent with the mass of the Higgs boson observed at the LHC, and we expect a local significance of 1.9 standard deviations. We separately combine searches for H→bb¯, H→W+W−, H→τ+τ−, and H→γγ. The observed signal strengths in all channels are consistent with the presence of a standard model Higgs boson with a mass of 125 GeV/c2.
15694618
Open N=2 strings in a B-field background and noncommutative self-dual Yang–Mills
Abstract In the presence of D-branes, fermionic N =2 strings in 2+2 dimensions can be coupled to a Kahler NS–NS two-form B . We present the corresponding action which produces N =2 supersymmetric boundary conditions and discuss the Seiberg–Witten zero-slope limit. After recalling the constraints on the Chan–Paton gauge group, we demonstrate for U ( n ) groups that the open N =2 string with a nonzero B -field coincides on tree level with noncommutative self-dual Yang–Mills. Several misconceptions of hep-th/0011206 are corrected.
56070963
Heterotic string plus five-brane systems with asymptotic $\mathrm{AdS}_3$
We present NS1+NS5-brane solutions of heterotic supergravity on curved geometries. They interpolate between a near horizon AdS3 × X k × T 7−k region and R 1,1 × c(X k ) × T 7−k , where X k (with k = 3,5,6,7) is a k-dimensional geometric Killing spinor manifold, c(X k ) its Ricciflat cone and T 7−k a (7 k)-torus. The solutions require first order � ′ -corrections to the field equations, and special point-like instantons play an important role, whose singular support is a calibrated submanifold wrapped by the NS5-brane. It is also possible to add a gauge anti-5brane. We determine the super isometries of the near horizon geometry which are supposed to appear as symmetries of the holographically dual two-dimensional conformal field theory.
14101499
BOUNCES/DYONS IN THE PLANE WAVE MATRIX MODEL AND SU(N) YANG–MILLS THEORY
We consider SU(N) Yang–Mills theory on the space ℝ × S3 with Minkowski signature (-+++). The condition of SO(4)-invariance imposed on gauge fields yields a bosonic matrix model which is a consistent truncation of the plane wave matrix model. For matrices parametrized by a scalar ϕ, the Yang–Mills equations are reduced to the equation of a particle moving in the double-well potential. The classical solution is a bounce, i.e. a particle which begins at the saddle point ϕ = 0 of the potential, bounces off the potential wall and returns to ϕ = 0. The gauge field tensor components parametrized by ϕ are smooth and for finite time, both electric and magnetic fields are nonvanishing. The energy density of this non-Abelian dyon configuration does not depend on coordinates of ℝ × S3 and the total energy is proportional to the inverse radius of S3. We also describe similar bounce dyon solutions in SU(N) Yang–Mills theory on the space ℝ × S2 with signature (-++). Their energy is proportional to the square of the inverse radius of S2. From the viewpoint of Yang–Mills theory on ℝ1,1 × S2 these solutions describe non-Abelian (dyonic) flux tubes extended along the x3-axis.
119253503
Integrable vortex-type equations on the two-sphere
We consider the Yang-Mills instanton equations on the four-dimensional manifold ${S}^{2}\ifmmode\times\else\texttimes\fi{}\ensuremath{\Sigma}$, where $\ensuremath{\Sigma}$ is a compact Riemann surface of genus $gg1$ or its covering space ${H}^{2}=\mathrm{SU}(1,1)/\mathrm{U}(1)$. Introducing a natural ansatz for the gauge potential, we reduce the instanton equations on ${S}^{2}\ifmmode\times\else\texttimes\fi{}\ensuremath{\Sigma}$ to vortex-type equations on the sphere ${S}^{2}$. It is shown that when the scalar curvature of the manifold ${S}^{2}\ifmmode\times\else\texttimes\fi{}\ensuremath{\Sigma}$ vanishes, the vortex-type equations are integrable, i.e., can be obtained as compatibility conditions of two linear equations (Lax pair), which are written down explicitly. Thus, the standard methods of integrable systems can be applied for constructing their solutions. However, even if the scalar curvature of ${S}^{2}\ifmmode\times\else\texttimes\fi{}\ensuremath{\Sigma}$ does not vanish, the vortex equations are well defined and have solutions for any values of the topological charge $N$. We show that any solution to the vortex equations on ${S}^{2}$ with a fixed topological charge $N$ corresponds to a Yang-Mills instanton on ${S}^{2}\ifmmode\times\else\texttimes\fi{}\ensuremath{\Sigma}$ of charge $(g\ensuremath{-}1)N$.
119261777
Neutron star's initial spin period distribution
We analyze different possibilities to explain the wide initial spin period distribution of radio pulsars presented by Noutsos et al. (2013). With a population synthesis modeling we demonstrate that magnetic field decay can be used to interpret the d ifference between the recent results by Noutsos et al. (2013) and those by Popov & Turolla (2012), where a much younger population of NSs associated with supernova remnants with known ages has been studied. In particular, an exponential field decay with τmag = 5 Myrs can produce a “tail” in the reconstructed initial spin period distribution (as obtained by N outsos et al. 2013) up to P0 > 1 s starting with a standard gaussian withh P0i= 0.3 s andσP = 0.15 s. Another option to explain the difference between initial spin period distributions from Noutsos et al. (2013) and Popov & Turolla (2012) — the emerging magnetic field — is also b riefly discussed.