D-wave superconductivity in doped Mott insulators

The effect of proximity to a Mott insulating phase on the charge transport properties of a superconductor is determined. An action describing the low energy physics is formulated and different scenarios for the approach to the Mott phase are distinguished by different variation with doping of the parameters in the action. A crucial issue is found to be the doping dependence of the quasiparticle charge which is defined here and which controls the temperature and field dependence of the electromagnetic response functions. Presently available data on high-T$_{c}$ superconductors are analysed. The data, while neither complete nor entirely consistent, suggest that neither the quasiparticle velocity nor the quasiparticle charge vanish as the Mott phase is approached, in contradiction to the predictions of several widely studied theories of lightly doped Mott insulators. Implications of the results for the structure of vortices in high-T$_{c}$ superconductors are determined. The numerical coefficients in the field-dependent specific heat are given for square and triangular vortex lattices.Comment: 12 pages. No figures. Submitted to JPCS (Proceedings of Chicago SNS conference

The High Magnetic Field Phase Diagram of a Quasi-One Dimensional Metal

We present a unique high magnetic field phase of the quasi-one dimensional organic conductor (TMTSF)$_2$ClO$_4$. This phase, termed "Q-ClO$_4$", is obtained by rapid thermal quenching to avoid ordering of the ClO$_4$ anion. The magnetic field dependent phase of Q-ClO$_4$ is distinctly different from that in the extensively studied annealed material. Q-ClO$_4$ exhibits a spin density wave (SDW) transition at $\approx$ 5 K which is strongly magnetic field dependent. This dependence is well described by the theoretical treatment of Bjelis and Maki. We show that Q-ClO$_4$ provides a new B-T phase diagram in the hierarchy of low-dimensional organic metals (one-dimensional towards two-dimensional), and describe the temperature dependence of the of the quantum oscillations observed in the SDW phase.Comment: 10 pages, 4 figures, preprin

Big, Fast Vortices in the d-RVB theory of High Temperature Superconductivity

The effect of proximity to a Mott insulating phase on the superflow properties of a d-wave superconductor is studied using the slave boson-U(1) gauge theory model. The model has two limits corresponding to superconductivity emerging either out of a 'renormalized fermi liquid' or out of a non-fermi-liquid regime. Three crucial physical parameters are identified: the size of the vortex \textit{as determined from the supercurrent it induces;} the coupling of the superflow to the quasiparticles and the 'nondissipative time derivative' term. As the Mott phase is approached, the core size as defined from the supercurrent diverges, the coupling between superflow and quasiparticles vanishes, and the magnitude of the nondissipative time derivative dramatically increases. The dissipation due to a moving vortex is found to vary as the third power of the doping. The upper critical field and the size of the critical regime in which paraconductivity may be observed are estimated, and found to be controlled by the supercurrent length scale

A Pure-Glue Hidden Valley I. States and Decays

It is possible that the standard model is coupled, through new massive charged or colored particles, to a hidden sector whose low energy dynamics is controlled by a pure Yang-Mills theory, with no light matter. Such a sector would have numerous metastable "hidden glueballs" built from the hidden gluons. These states would decay to particles of the standard model. We consider the phenomenology of this scenario, and find formulas for the lifetimes and branching ratios of the most important of these states. The dominant decays are to two standard model gauge bosons, or by radiative decays with photon emission, leading to jet- and photon-rich signals.Comment: 34 pages, 4 figure

Search for fourth generation quarks and leptons at the Fermilab Tevatron and CERN Large Hadron Collider

If next generations of heavy quarks and leptons exist within the standard model (SM), they can manifest themselves in Higgs boson production at the Tevatron and the LHC, before being actually observed. This generation leads to an increase of the Higgs boson production cross section via gluon fusion at hadron colliders by a factor 6-9. So, the study of this process at the Tevatron and LHC can finally fix the number of generations in the SM. Using the $WW^*$ Higgs boson decay channel, the studies at the upgraded Tevatron will answer the question about the next generation for mass values 135 GeV \lsim M_H\lsim 190 GeV. Studying the $\tau\bar{\tau}$ channel we show its large potential for the study of the Higgs boson at the LHC even in the standard case of three generations. At the Tevatron, studies in this channel could explore the mass range 110-140 GeV.Comment: 13 pages, 4 figures, LaTeX/RevTeX, final version accepted for publicatio

Interplay of Electron-Phonon Interaction and Electron Correlation in High Temperature Superconductivity

We study the electron-phonon interaction in the strongly correlated superconducting cuprates. Two types of the electron-phonon interactions are introduced in the $t-J$ model; the diagonal and off-diagonal interactions which modify the formation energy of the Zhang-Rice singlet and its transfer integral, respectively. The characteristic phonon-momentum $(\vec q)$ and electron-momentum $(\vec k)$ dependence resulted from the off-diagonal coupling can explain a variety of experiments. The vertex correction for the electron-phonon interaction is formulated in the SU(2) slave-boson theory by taking into account the collective modes in the superconducting ground states. It is shown that the vertex correction enhances the attractive potential for the d-wave paring mediated by phonon with $\vec q=(\pi(1-\delta), 0)$ around $\delta \cong 0.3$ which corresponds to the half-breathing mode of the oxygen motion.Comment: 14 pages, 13 figure

Search for direct production of charginos and neutralinos in events with three leptons and missing transverse momentum in √s = 7 TeV pp collisions with the ATLAS detector

A search for the direct production of charginos and neutralinos in final states with three electrons or muons and missing transverse momentum is presented. The analysis is based on 4.7 fb−1 of proton–proton collision data delivered by the Large Hadron Collider and recorded with the ATLAS detector. Observations are consistent with Standard Model expectations in three signal regions that are either depleted or enriched in Z-boson decays. Upper limits at 95% confidence level are set in R-parity conserving phenomenological minimal supersymmetric models and in simplified models, significantly extending previous results

Jet size dependence of single jet suppression in lead-lead collisions at sqrt(s(NN)) = 2.76 TeV with the ATLAS detector at the LHC

Measurements of inclusive jet suppression in heavy ion collisions at the LHC provide direct sensitivity to the physics of jet quenching. In a sample of lead-lead collisions at sqrt(s) = 2.76 TeV corresponding to an integrated luminosity of approximately 7 inverse microbarns, ATLAS has measured jets with a calorimeter over the pseudorapidity interval |eta| < 2.1 and over the transverse momentum range 38 < pT < 210 GeV. Jets were reconstructed using the anti-kt algorithm with values for the distance parameter that determines the nominal jet radius of R = 0.2, 0.3, 0.4 and 0.5. The centrality dependence of the jet yield is characterized by the jet "central-to-peripheral ratio," Rcp. Jet production is found to be suppressed by approximately a factor of two in the 10% most central collisions relative to peripheral collisions. Rcp varies smoothly with centrality as characterized by the number of participating nucleons. The observed suppression is only weakly dependent on jet radius and transverse momentum. These results provide the first direct measurement of inclusive jet suppression in heavy ion collisions and complement previous measurements of dijet transverse energy imbalance at the LHC.Comment: 15 pages plus author list (30 pages total), 8 figures, 2 tables, submitted to Physics Letters B. All figures including auxiliary figures are available at http://atlas.web.cern.ch/Atlas/GROUPS/PHYSICS/PAPERS/HION-2011-02

Two-Loop O(alpha_s G_F M_Q^2) Heavy-Quark Corrections to the Interactions between Higgs and Intermediate Bosons

By means of a low-energy theorem, we analyze at O(alpha_s G_F M_Q^2) the shifts in the Standard-Model W^+W^-H and ZZH couplings induced by virtual high-mass quarks, Q, with M_Q >> M_Z, M_H, which includes the top quark. Invoking the improved Born approximation, we then find the corresponding corrections to various four- and five-point Higgs-boson production and decay processes which involve the W^+W^-H and ZZH vertices with one or both of the gauge bosons being connected to light-fermion currents, respectively. This includes e^+e^- -> f anti-f H via Higgs-strahlung, via W^+W^- fusion (with f = nu_e), and via ZZ fusion (with f = e), as well as H -> 2V -> 4f (with V = W, Z).Comment: 20 pages (Latex); Physical Review D (to appear