Publications (213)595.83 Total impact
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ABSTRACT: We focus on a holographic approach to DIS at smallx in high energy where scattering is dominated by exchanging a Reggeized Graviton in $AdS_5$. We emphasize the importance of confinement, which corresponds to a deformation of $AdS_5$ geometry in the IR. This approach provides an excellent fit to the combined HERA data at small $x$. We also discuss the connection of Pomeron/Odderon intercepts in the conformal limit with anomalous dimensions in strong coupling.  [Show abstract] [Hide abstract]
ABSTRACT: We calculate the spinindependent scattering cross section for direct detection that results from the electromagnetic polarizability of a composite scalar baryon dark matter candidate  "Stealth Dark Matter", that is based on a dark SU(4) confining gauge theory. In the nonrelativistic limit, electromagnetic polarizability proceeds through a dimension7 interaction leading to a very small scattering cross section for dark matter with weak scale masses. This represents a lower bound on the scattering cross section for composite dark matter theories with electromagnetically charged constituents. We carry out lattice calculations of the polarizability for the lightest baryons in SU(3) and SU(4) gauge theories using the background field method on quenched configurations. We find the polarizabilities of SU(3) and SU(4) to be comparable (within about 50%) normalized to the baryon mass, which is suggestive for extensions to larger SU(N) groups. The resulting scattering cross sections with a xenon target are shown to be potentially detectable in the dark matter mass range of about 200700 GeV, where the lower bound is from the existing LUX constraint while the upper bound is the coherent neutrino background. Significant uncertainties in the cross section remain due to the more complicated interaction of the polarizablity operator with nuclear structure, however the steep dependence on the dark matter mass, $1/m_B^6$, suggests the observable dark matter mass range is not appreciably modified. We briefly highlight collider searches for the mesons in the theory as well as the indirect astrophysical effects that may also provide excellent probes of stealth dark matter.  [Show abstract] [Hide abstract]
ABSTRACT: We present a new model of "Stealth Dark Matter": a composite baryonic scalar of an $SU(N_D)$ stronglycoupled theory with even $N_D \geq 4$. All mass scales are technically natural, and dark matter stability is automatic without imposing an additional discrete or global symmetry. Constituent fermions transform in vectorlike representations of the electroweak group that permit both electroweakbreaking and electroweakpreserving mass terms. This gives a tunable coupling of stealth dark matter to the Higgs boson independent of the dark matter mass itself. We specialize to $SU(4)$, and investigate the constraints on the model from dark meson decay, electroweak precision measurements, basic collider limits, and spinindependent direct detection scattering through Higgs exchange. We exploit our earlier lattice simulations that determined the composite spectrum as well as the effective Higgs coupling of stealth dark matter in order to place bounds from direct detection, excluding constituent fermions with dominantly electroweakbreaking masses. A lower bound on the dark baryon mass $m_B \gtrsim 300$ GeV is obtained from the indirect requirement that the lightest dark meson not be observable at LEP II. We briefly survey some intriguing properties of stealth dark matter that are worthy of future study, including: collider studies of dark meson production and decay; indirect detection signals from annihilation; relic abundance estimates for both symmetric and asymmetric mechanisms; and direct detection through electromagnetic polarizability, a detailed study of which will appear in a companion paper.  [Show abstract] [Hide abstract]
ABSTRACT: We investigate the softwall AdS/CFT model. We specifically looked at the Pomeron, leading Regge contribution to a scattering process and used it to fit deep inelastic scattering data from the HERA collaboration. We find that the model fits the data with much more success than the purely conformal case, and find similar success to previous confinement models.  [Show abstract] [Hide abstract]
ABSTRACT: We investigate the transition between spontaneous chiral symmetry breaking and conformal behavior in the SU(3) theory with multiple fermion flavors. We propose a new strategy for studying this transition. Instead of changing the number of flavors, we lift the mass of a subset of the fermions, keeping the rest of the fermions near to the massless chiral limit in order to probe the transition. Dedicated to the 60th birthday of Academician Valery Rubakov.Journal of Experimental and Theoretical Physics 10/2014; 120(3). DOI:10.1134/S1063776115030176 · 0.88 Impact Factor  [Show abstract] [Hide abstract]
ABSTRACT: From the perspective of AdS/CFT the Pomeron is identified with a Reggeized Graviton, while the Odderons correspond to Reggeized antisymmetric $AdS_5$ KalbRamond tensorfields. In this paper, we consider the strong coupling expansion of the dimension of the leading twist operators dual to these Regge trajectories, $\Delta(j)$, to determine its analytic continuation in $j$ beyond the diffusion limit. In particular, we compute the strong coupling expansion of the intercept to order $\lambda^{3}$, where $\lambda$ is the t'Hooft coupling, for both the Pomeron, which is $C=+1$ crossingeven, and the "Odderons", which are the leading $C=1$ crossingodd Regge singularities. We discuss the spectral curves of the class of singletrace operators to which these string modes couple.Journal of High Energy Physics 09/2014; 2015(2). DOI:10.1007/JHEP02(2015)104 · 6.11 Impact Factor 
Article: Improved Lattice Radial Quantization
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ABSTRACT: Lattice radial quantization was proposed in a recent paper by Brower, Fleming and Neuberger[1] as a nonperturbative method especially suited to numerically solve Euclidean conformal field theories. The lessons learned from the lattice radial quantization of the 3D Ising model on a longitudinal cylinder with 2D Icosahedral crosssection suggested the need for an improved discretization. We consider here the use of the Finite Element Methods(FEM) to descretize the universallyequivalent $\phi^4$ Lagrangian on $\mathbb R \times \mathbb S^2$. It is argued that this lattice regularization will approach the exact conformal theory at the WilsonFisher fixed point in the continuum. Numerical tests are underway to support this conjecture.  [Show abstract] [Hide abstract]
ABSTRACT: We study an SU(3) gauge theory with Nf=8 degenerate flavors of light fermions in the fundamental representation. Using the domain wall fermion formulation, we investigate the light hadron spectrum, chiral condensate and electroweak S parameter. We consider a range of light fermion masses on two lattice volumes at a single gauge coupling chosen so that IR scales approximately match those from our previous studies of the two and sixflavor systems. Our results for the Nf=8 spectrum suggest spontaneous chiral symmetry breaking, though fits to the fermion mass dependence of spectral quantities do not strongly disfavor the hypothesis of massdeformed infrared conformality. Compared to Nf=2 we observe a significant enhancement of the chiral condensate relative to the symmetry breaking scale F, similar to the situation for Nf=6. The reduction of the S parameter, related to parity doubling in the vector and axialvector channels, is also comparable to our sixflavor results.Physical Review D 05/2014; 90(11). DOI:10.1103/PhysRevD.90.114502 · 4.64 Impact Factor  [Show abstract] [Hide abstract]
ABSTRACT: Using lattice simulations, we study the infrared behavior of a particularly interesting SU(2) gauge theory, with six massless Dirac fermions in the fundamental representation. We compute the running gauge coupling derived nonperturbatively from the Schrödinger functional of the theory, finding no evidence for an infrared fixed point up through gauge couplings g¯2 of order 20. This implies that the theory either is governed in the infrared by a fixed point of considerable strength, unseen so far in nonsupersymmetric gauge theories, or breaks its global chiral symmetries producing a large number of composite NambuGoldstone bosons relative to the number of underlying degrees of freedom. Thus either of these phases exhibits novel behavior.Physical Review Letters 03/2014; 112(11):111601. DOI:10.1103/PhysRevLett.112.111601 · 7.51 Impact Factor  [Show abstract] [Hide abstract]
ABSTRACT: We present a novel technique for the determination of the topological susceptibility (related to the variance of the distribution of global topological charge) from lattice gauge theory simulations, based on maximumlikelihood analysis of the Markovchain Monte Carlo time series. This technique is expected to be particularly useful in situations where relatively few tunneling events are observed. Restriction to a lattice subvolume on which topological charge is not quantized is explored, and may lead to further improvement when the global topology is poorly sampled. We test our proposed method on a set of lattice data, and compare it to traditional methods.Physical Review D 03/2014; 90(1). DOI:10.1103/PhysRevD.90.014503 · 4.64 Impact Factor  [Show abstract] [Hide abstract]
ABSTRACT: We present the spectrum of baryons in a new SU(4) gauge theory with fundamental fermion constituents. The spectrum of these bosonic baryons is of significant interest for composite dark matter theories. Here, we compare the spectrum and properties of SU(3) and SU(4) baryons, and then compute the darkmatter direct detection cross section via Higgs boson exchange for TeVscale composite dark matter arising from a confining SU(4) gauge sector. Comparison with the latest LUX results leads to tight bounds on the fraction of the constituentfermion mass that may arise from electroweak symmetry breaking. Lattice calculations of the dark matter mass spectrum and the Higgsdark matter coupling are performed on quenched $16^{3} \times 32$, $32^{3} \times 64$, $48^{3} \times 96$, and $64^{3} \times128$ lattices with three different lattice spacings, using Wilson fermions with moderate to heavy pseudoscalar meson masses. Our results lay a foundation for future analytic and numerical study of composite baryonic dark matter.Physical Review D 02/2014; 89(9). DOI:10.1103/PhysRevD.89.094508 · 4.64 Impact Factor  [Show abstract] [Hide abstract]
ABSTRACT: We discuss how exact conformal invariance in the strong coupling leads naturally through AdS/CFT correspondence to a systematic expansion for the Pomeron and Odderon intercepts in power of $\lambda^{1/2}$, with $\lambda=g^2N_c$ the 't Hooft coupling. We also point out the importance of confinement for a realistic treatment of DIS in the HERA energy range.  [Show abstract] [Hide abstract]
ABSTRACT: This is the report of the Computing Frontier working group on Lattice Field Theory prepared for the proceedings of the 2013 Community Summer Study ("Snowmass"). We present the future computing needs and plans of the U.S. lattice gauge theory community and argue that continued support of the U.S. (and worldwide) latticeQCD effort is essential to fully capitalize on the enormous investment in the highenergy physics experimental program. We first summarize the dramatic progress of numerical latticeQCD simulations in the past decade, with some emphasis on calculations carried out under the auspices of the U.S. LatticeQCD Collaboration, and describe a broad program of latticeQCD calculations that will be relevant for future experiments at the intensity and energy frontiers. We then present details of the computational hardware and software resources needed to undertake these calculations.  [Show abstract] [Hide abstract]
ABSTRACT: This White Paper has been prepared as a planning document for the Division of High Energy Physics of the U. S. Department of Energy. Recent progress in latticebased studies of physics beyond the standard model is summarized, and major current goals of USQCD research in this area are presented. Challenges and opportunities associated with the recently discovered 126 GeV Higgslike particle are highlighted. Computational resources needed for reaching important goals are described. The document was finalized on February 11, 2013 with references that are not aimed to be complete, or account for an accurate historical record of the field.  [Show abstract] [Hide abstract]
ABSTRACT: Composite dark matter candidates, which can arise from new stronglycoupled sectors, are wellmotivated and phenomenologically interesting, particularly in the context of asymmetric generation of the relic density. In this work, we employ lattice calculations to study the electromagnetic form factors of electroweakneutral darkmatter baryons for a threecolor, QCDlike theory with Nf = 2 and 6 degenerate fermions in the fundamental representation. We calculate the (connected) charge radius and anomalous magnetic moment, both of which can play a significant role for direct detection of composite dark matter. We find minimal Nf dependence in these quantities. We generate massdependent crosssections for dark matternucleon interactions and use them in conjunction with experimental results from XENON100, excluding dark matter candidates of this type with masses below 10 TeV.Physical review D: Particles and fields 01/2013; 88(1). DOI:10.1103/PhysRevD.88.014502 · 4.86 Impact Factor  [Show abstract] [Hide abstract]
ABSTRACT: Lattice radial quantization is introduced as a nonperturbative method intended to numerically solve Euclidean conformal field theories that can be realized as fixed points of known Lagrangians. As an example, we employ a lattice shaped as a cylinder with a 2D Icosahedral crosssection to discretize dilatations in the 3D Ising model. Using the integer spacing of the anomalous dimensions of the first two descendants ( ), we obtain an estimate for . We also observed small deviations from integer spacing for the 3rd descendant, which suggests that a further improvement of our radial lattice action will be required to guarantee conformal symmetry at the WilsonFisher fixed point in the continuum limit.Physics Letters B 12/2012; 721(s 4–5). DOI:10.1016/j.physletb.2013.03.009 · 6.13 Impact Factor  [Show abstract] [Hide abstract]
ABSTRACT: We consider radial quantization for conformal quantum field theory with a lattice regulator. A Euclidean field theory on $\mathbb R^D$ is mapped to a cylindrical manifold, $\mathbb R\times \mathbb S^{D1}$, whose length is logarithmic in scale separation. To test the approach, we apply this to the 3D Ising model and compute $\eta$ for the first $Z_2$ odd primary operator. 
Article: The KalbRamond Odderon in AdS/CFT
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ABSTRACT: At high energies, elastic hadronic cross sections, such as pp, pp, �±p, are domi nated by vacuum exchange, which in leading order of the 1/Nc expansion has been identified as the BFKL Pomeron or its strong AdS dual the closed string Reggeized graviton (1). However the difference of particle antiparticle cross sections are given by a socalled Odderon, carrying C = 1 vacuum quantum numbers identified in weak coupling with odd numbers of exchanged gluons. Here we show that in the dual description the Odderon is the Reggeized KalbRamond field (B�ν ) in the NeveuSchwartz sector of closed string theory. To first order in strong coupling, the high energy contribution of Odderon is evaluated for N = 4 Super YangMills by a generalization of the gravity dual analysis for Pomeron in Ref. (1). The con sequence of confinement on the Odderon are estimated in the confining QCDlike AdS5 hardwall model of Polchinski and Strassler (2).  [Show abstract] [Hide abstract]
ABSTRACT: In the past decade overwhelming evidence has emerged for a conjectured duality between a wide class of gauge theories in d dimensions and string theories on asymptotically AdS_{d+1} spaces. We apply this duality to scattering processes that occur via Pomeron exchange. First we develop the Pomeron in string theory, as done by Brower, Polchinski, Strassler and Tan, showing that it naturally emerges as the Regge Trajectory of the AdS graviton. Next we apply the AdS Pomeron to the study of Deeply Virtual Compton Scattering (DVCS), and see that our model gives good results when compared to HERA data. We then show how we can extend our results to double Pomeron exchange, and apply it to developing a formalism for the study of double diffractive Higgs production.  [Show abstract] [Hide abstract]
ABSTRACT: We present a review of the properties of generalized domain wall Fermions, based on a (real) M\"obius transformation on the Wilson overlap kernel, discussing their algorithmic efficiency, the degree of explicit chiral violations measured by the residual mass ($m_{res}$) and the WardTakahashi identities. The M\"obius class interpolates between Shamir's domain wall operator and Bori\c{c}i's domain wall implementation of Neuberger's overlap operator without increasing the number of Dirac applications per conjugate gradient iteration. A new scaling parameter ($\alpha$) reduces chiral violations at finite fifth dimension ($L_s$) but yields exactly the same overlap action in the limit $L_s \rightarrow \infty$. Through the use of 4d Red/Black preconditioning and optimal tuning for the scaling $\alpha(L_s)$, we show that chiral symmetry violations are typically reduced by an order of magnitude at fixed $L_s$. At large $L_s$ we argue that the observed scaling for $m_{res} = O(1/L_s)$ for Shamir is replaced by $m_{res} = O(1/L_s^2)$ for the properly tuned M\"obius algorithm with $\alpha = O(L_s)$
Publication Stats
4k  Citations  
595.83  Total Impact Points  
Top Journals
Institutions

1987–2015

Boston University
 Department of Physics
Boston, Massachusetts, United States


2010

Brown University
 Department of Physics
Providence, Rhode Island, United States


2003

Bergische Universität Wuppertal
Wuppertal, North RhineWestphalia, Germany


1971–2002

Massachusetts Institute of Technology
 • Laboratory for Nuclear Science
 • Center for Theoretical Physics
Cambridge, Massachusetts, United States


1987–1994

University of Massachusetts Boston
 Department of Physics
Boston, Massachusetts, United States


1989–1992

Dalhousie University
Halifax, Nova Scotia, Canada


1985

City College of New York
 Department of Physics
New York City, NY, United States


1984

Rutgers, The State University of New Jersey
 Department of Physics
НьюБрансуик, New Jersey, United States


1981–1984

Harvard University
 Department of Physics
Cambridge, Massachusetts, United States


1974–1984

University of California, Santa Cruz
 • Institute for Particle Physics
 • Department of Physics
Santa Cruz, California, United States


1978

University of California Observatories
Santa Cruz, California, United States


1976–1977

CERN
Genève, Geneva, Switzerland


1973

California Institute of Technology
Pasadena, California, United States


1967–1970

University of California, Berkeley
 Department of Physics
Berkeley, California, United States
