Higgs production in CP-violating supersymmetric cascade decays: probing the `open hole' at the Large Hadron Collider

A benchmark CP-violating supersymmetric scenario (known as 'CPX-scenario' in the literature) is studied in the context of the Large Hadron Collider (LHC). It is shown that the LHC, with low to moderate accumulated luminosity, will be able to probe the existing `hole' in the $m_{h_1}$-$\tan\beta$ plane, which cannot be ruled out by the LEP data. We explore the parameter space with cascade decay of third generation squarks and gluino with CP-violating decay branching fractions. We propose a multi-channel analysis to probe this parameter space some of which are background free at an integrated luminosity of 5-10 fb$^{-1}$. Specially, multi-lepton final states (3\l,\, 4\l and like sign di-lepton) are almost background free and have $5\sigma$ reach for the corresponding signals with very early data of LHC for both 14 TeV and 7 TeV center of mass energy.Comment: 24 pages, 9 figures, references added as in the journal versio

Facile Synthesis of High Quality Graphene Nanoribbons

Graphene nanoribbons have attracted attention for their novel electronic and spin transport properties1-6, and because nanoribbons less than 10 nm wide have a band gap that can be used to make field effect transistors. However, producing nanoribbons of very high quality, or in high volumes, remains a challenge. Here, we show that pristine few-layer nanoribbons can be produced by unzipping mildly gas-phase oxidized multiwalled carbon nanotube using mechanical sonication in an organic solvent. The nanoribbons exhibit very high quality, with smooth edges (as seen by high-resolution transmission electron microscopy), low ratios of disorder to graphitic Raman bands, and the highest electrical conductance and mobility reported to date (up to 5e2/h and 1500 cm2/Vs for ribbons 10-20 nm in width). Further, at low temperature, the nanoribbons exhibit phase coherent transport and Fabry-Perot interference, suggesting minimal defects and edge roughness. The yield of nanoribbons was ~2% of the starting raw nanotube soot material, which was significantly higher than previous methods capable of producing high quality narrow nanoribbons1. The relatively high yield synthesis of pristine graphene nanoribbons will make these materials easily accessible for a wide range of fundamental and practical applications.Comment: Nature Nanotechnology in pres

Experimental investigation of classical and quantum correlations under decoherence

It is well known that many operations in quantum information processing depend largely on a special kind of quantum correlation, that is, entanglement. However, there are also quantum tasks that display the quantum advantage without entanglement. Distinguishing classical and quantum correlations in quantum systems is therefore of both fundamental and practical importance. In consideration of the unavoidable interaction between correlated systems and the environment, understanding the dynamics of correlations would stimulate great interest. In this study, we investigate the dynamics of different kinds of bipartite correlations in an all-optical experimental setup. The sudden change in behaviour in the decay rates of correlations and their immunity against certain decoherences are shown. Moreover, quantum correlation is observed to be larger than classical correlation, which disproves the early conjecture that classical correlation is always greater than quantum correlation. Our observations may be important for quantum information processing.Comment: 7 pages, 4 figures, to appear in Nature Communication

Search for Higgs bosons of the Universal Extra Dimensions at the Large Hadron Collider

The Higgs sector of the Universal Extra Dimensions (UED) has a rather involved setup. With one extra space dimension, the main ingredients to the construct are the higher Kaluza-Klein (KK) excitations of the Standard Model Higgs boson and the fifth components of the gauge fields which on compactification appear as scalar degrees of freedom and can mix with the former thus leading to physical KK-Higgs states of the scenario. In this work, we explore in detail the phenomenology of such a Higgs sector of the UED with the Large Hadron Collider (LHC) in focus. We work out relevant decay branching fractions involving the KK-Higgs excitations. Possible production modes of the KK-Higgs bosons are then discussed with an emphasis on their associated production with the third generation KK-quarks and that under the cascade decays of strongly interacting UED excitations which turn out to be the only phenomenologically significant modes. It is pointed out that the collider searches of such Higgs bosons face generic hardship due to soft end-products which result from severe degeneracies in the masses of the involved excitations in the minimal version of the UED (MUED). Generic implications of either observing some or all of the KK-Higgs bosons at the LHC are discussed.Comment: 25 pages, 9 figures and 1 tabl

Large CP Violation in B_s Meson Mixing with EDM constraint in Supersymmetry

Motivated by the recent measurement of the like-sign dimuon charge asymmetry, we investigate anomalous CP violation in the B_s- bar{B}_s mixing within the supersymmetry. We show that when gluino diagrams dominate supersymmetry contributions, it is very difficult to realize a large B_s- bar{B}_s mixing phase under the constraint from electric dipole moments barring cancellations. This constraint can be ameliorated by supposing superparticles decoupled. In this limit, we find that it is possible to achieve the large CP asymmetry, and the branching ratio of B_s -> mu^+ mu^- tends to become sizable.Comment: 20 pages, 5 figure

Detection of the pairwise kinematic Sunyaev-Zel'dovich effect with BOSS DR11 and the Atacama Cosmology Telescope

We present a new measurement of the kinematic Sunyaev-Zeldovich effect using data from the Atacama Cosmology Telescope (ACT) and the Baryon Oscillation Spectroscopic Survey (BOSS). Using 600 square degrees of overlapping sky area, we evaluate the mean pairwise baryon momentum associated with the positions of 50,000 bright galaxies in the BOSS DR11 Large Scale Structure catalog. A non-zero signal arises from the large-scale motions of halos containing the sample galaxies. The data fits an analytical signal model well, with the optical depth to microwave photon scattering as a free parameter determining the overall signal amplitude. We estimate the covariance matrix of the mean pairwise momentum as a function of galaxy separation, using microwave sky simulations, jackknife evaluation, and bootstrap estimates. The most conservative simulation-based errors give signal-to-noise estimates between 3.6 and 4.1 for varying galaxy luminosity cuts. We discuss how the other error determinations can lead to higher signal-to-noise values, and consider the impact of several possible systematic errors. Estimates of the optical depth from the average thermal Sunyaev-Zeldovich signal at the sample galaxy positions are broadly consistent with those obtained from the mean pairwise momentum signal.Comment: 15 pages, 8 figures, 2 table

Bipolar supercurrent in graphene

Graphene -a recently discovered one-atom-thick layer of graphite- constitutes a new model system in condensed matter physics, because it is the first material in which charge carriers behave as massless chiral relativistic particles. The anomalous quantization of the Hall conductance, which is now understood theoretically, is one of the experimental signatures of the peculiar transport properties of relativistic electrons in graphene. Other unusual phenomena, like the finite conductivity of order 4e^2/h at the charge neutrality (or Dirac) point, have come as a surprise and remain to be explained. Here, we study the Josephson effect in graphene. Our experiments rely on mesoscopic superconducting junctions consisting of a graphene layer contacted by two closely spaced superconducting electrodes, where the charge density can be controlled by means of a gate electrode. We observe a supercurrent that, depending on the gate voltage, is carried by either electrons in the conduction band or by holes in the valence band. More importantly, we find that not only the normal state conductance of graphene is finite, but also a finite supercurrent can flow at zero charge density. Our observations shed light on the special role of time reversal symmetry in graphene and constitute the first demonstration of phase coherent electronic transport at the Dirac point.Comment: Under review, 12 pages, 4 Figs., suppl. info (v2 identical, resolved file problems

Quantum Discord and entropic measures of quantum correlations: Optimization and behavior in finite XYXY spin chains

We discuss a generalization of the conditional entropy and one-way information deficit in quantum systems, based on general entropic forms. The formalism allows to consider simple entropic forms for which a closed evaluation of the associated optimization problem in qudit-qubit systems is shown to become feasible, allowing to approximate that of the quantum discord. As application, we examine quantum correlations of spin pairs in the exact ground state of finite $XY$ spin chains in a magnetic field through the quantum discord and information deficit. While these quantities show a similar behavior, their optimizing measurements exhibit significant differences, which can be understood and predicted through the previous approximations. The remarkable behavior of these quantities in the vicinity of transverse and non-transverse factorizing fields is also discussed.Comment: 10 pages, 3 figure

Gaugino Anomaly Mediated SUSY Breaking: phenomenology and prospects for the LHC

We examine the supersymmetry phenomenology of a novel scenario of supersymmetry (SUSY) breaking which we call Gaugino Anomaly Mediation, or inoAMSB. This is suggested by recent work on the phenomenology of flux compactified type IIB string theory. The essential features of this scenario are that the gaugino masses are of the anomaly-mediated SUSY breaking (AMSB) form, while scalar and trilinear soft SUSY breaking terms are highly suppressed. Renormalization group effects yield an allowable sparticle mass spectrum, while at the same time avoiding charged LSPs; the latter are common in models with negligible soft scalar masses, such as no-scale or gaugino mediation models. Since scalar and trilinear soft terms are highly suppressed, the SUSY induced flavor and CP-violating processes are also suppressed. The lightest SUSY particle is the neutral wino, while the heaviest is the gluino. In this model, there should be a strong multi-jet +etmiss signal from squark pair production at the LHC. We find a 100 fb^{-1} reach of LHC out to m_{3/2}\sim 118 TeV, corresponding to a gluino mass of \sim 2.6 TeV. A double mass edge from the opposite-sign/same flavor dilepton invariant mass distribution should be visible at LHC; this, along with the presence of short-- but visible-- highly ionizing tracks from quasi-stable charginos, should provide a smoking gun signature for inoAMSB.Comment: 30 pages including 14 .eps figure

A fourth generation, anomalous like-sign dimuon charge asymmetry and the LHC

A fourth chiral generation, with $m_{t^\prime}$ in the range $\sim (300 - 500)$ GeV and a moderate value of the CP-violating phase can explain the anomalous like-sign dimuon charge asymmetry observed recently by the D0 collaboration. The required parameters are found to be consistent with constraints from other $B$ and $K$ decays. The presence of such quarks, apart from being detectable in the early stages of the LHC, would also have important consequences in the electroweak symmetry breaking sector.Comment: 18 pages, 9 figures, Figure 1 is modified, more discussions are added in section 2. new references adde