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Emanuel Katz

Publications and source records attributed to Emanuel Katz.

At least 55 records · Page 3Linked to original sources
arXiv2009

A Simple Explanation for DAMA with Moderate Channeling

We consider the possibility that the DAMA signal arises from channeled events in simple models where the dark matter interaction with nuclei is suppressed at small momenta. As with the standard WIMP, these models have two parameters (the dark matter mass and the size of the cross-section), without the need to introduce an additional energy threshold type of parameter. We find that they can be consistent with channeling fractions as low as about ~ 15%, so long as at least ~70% of the nuclear recoil energy for channeled events is deposited electronically. Given that there are reasons not to expect very large channeling fractions, these scenarios make the channeling explanation of DAMA much more compelling.

hep-ph↗
arXiv2009

The 't Hooft Model As A Hologram

We consider the 3d dual of 1+1 dimensional large-N_c QCD with quarks in the fundamental representation, also known as the 't Hooft model. 't Hooft solved this model by deriving a Schroedinger equation for the wavefunction of a parton inside the meson. In the scale-invariant limit, we show how this equation is related by a transform to the equation of motion for a scalar field in AdS_3. We thus find an explicit map between the `parton-x' variable and the radial coordinate of AdS_3. This direct map allows us to check the AdS/CFT prescription from the 2d side. We describe various features of the dual in the conformal limit and to the leading order in conformal symmetry breaking, and make some comments on the 3d theory in the fully non-conformal regime.

hep-th↗
arXiv2008

A composite gluino at the LHC

We investigate the decay of particles with the quantum numbers of the gluino. Besides SUSY, such particles may be present in models where the Higgs and top are composite. We find that such 'composite' gluinos have decay signatures similar to those of gluinos in 'more minimal' SUSY type models. Though it is in principle possible to distinguish the two scenarios, we find that it will be a challenging task at the LHC. This puts into question the common lore that a gluino is an obvious 'smoking-gun' signature of SUSY.

hep-ph↗
arXiv2007

An Eta Primer: Solving the U(1) Problem with AdS/QCD

Inspired by the AdS/CFT correspondence, we study the pseudoscalar mesons of QCD through a dual embedding in a strongly curved extra dimensional spacetime. This model incorporates the consequences of symmetry and has very few free parameters, due to constraints from five-dimensions and the operator product expansion of QCD. Using as inputs the pion, kaon, and rho masses and fpi, we compute the eta and eta prime masses to be 520 and 867 MeV, respectively. Their decay rates into photons are also computed and found to be in good agreement with data.

hep-ph↗
arXiv2007

Tensors Mesons in AdS/QCD

We explore tensor mesons in AdS/QCD focusing on f2 (1270), the lightest spin-two resonance in QCD. We find that the f2 mass and the partial width for f2 -> gamma gamma are in very good agreement with data. In fact, the dimensionless ratio of these two quantities comes out within the current experimental bound. The result for this ratio depends only on Nc and Nf, and the quark and glueball content of the operator responsible for the f2; more importantly, it does not depend on chiral symmetry breaking and so is both independent of much of the arbitrariness of AdS/QCD and completely out of reach of chiral perturbation theory. For comparison, we also explore f2 -> pi pi, which because of its sensitivity to the UV corrections has much more uncertainty. We also calculate the masses of the higher spin resonances on the Regge trajectory of the f2, and find they compare favorably with experiment.

hep-ph↗
arXiv2006

Linear Confinement and AdS/QCD

In a theory with linear confinement, such as QCD, the masses squared m^2 of mesons with high spin S or high radial excitation number n are expected, from semiclassical arguments, to grow linearly with S and n. We show that this behavior can be reproduced within a putative 5-dimensional theory holographically dual to QCD (AdS/QCD). With the assumption that such a dual theory exists and describes highly excited mesons as well, we show that asymptotically linear m^2 spectrum translates into a strong constraint on the INFRARED behavior of that theory. In the simplest model which obeys such a constraint we find m^2 ~ (n+S).

hep-ph↗
arXiv2005

QCD and a Holographic Model of Hadrons

We propose a five-dimensional framework for modeling low-energy properties of QCD. In the simplest three parameter model we compute masses, decay rates and couplings of the lightest mesons. The model fits experimental data to within 10%. The framework is a holographic version of the QCD sum rules, motivated by the anti-de Sitter/conformal field theory (AdS/CFT) correspondence. The model naturally incorporates properties of QCD dictated by chiral symmetry, which we demonstrate by deriving the Gell-Mann-Oakes-Renner relationship for the pion mass.

hep-ph↗
arXiv2005

A Composite Little Higgs Model

We describe a natural UV complete theory with a composite little Higgs. Below a TeV we have the minimal Standard Model with a light Higgs, and an extra neutral scalar. At the TeV scale there are additional scalars, gauge bosons, and vector-like charge 2/3 quarks, whose couplings to the Higgs greatly reduce the UV sensitivity of the Higgs potential. Stabilization of the Higgs mass squared parameter, without finetuning, occurs due to a softly broken shift symmetry--the Higgs is a pseudo Nambu-Goldstone boson. Above the 10 TeV scale the theory has new strongly coupled interactions. A perturbatively renormalizable UV completion, with softly broken supersymmetry at 10 TeV is explicitly worked out. Our theory contains new particles which are odd under an exact "dark matter parity", (-1)^{(2S+3B+L)}. We argue that such a parity is likely to be a feature of many theories of new TeV scale physics. The lightest parity odd particle, or "LPOP", is most likely a neutral fermion, and may make a good dark matter candidate, with similar experimental signatures to the neutralino of the MSSM. We give a general effective field theory analysis of the calculation of corrections to precision electroweak observables.

hep-ph↗
arXiv2005

The Intermediate Higgs

Two paradigms for the origin of electroweak superconductivity are a weakly coupled scalar condensate, and a strongly coupled fermion condensate. The former suffers from a finetuning problem unless there are cancelations to radiative corrections, while the latter presents potential discrepancies with precision electroweak physics. Here we present a framework for electroweak symmetry breaking which interpolates between these two paradigms, and mitigates their faults. As in Little Higgs theories, the Higgs is a pseudo-Nambu Goldstone boson, potentially composite. The cutoff sensitivity of the one loop top quark contribution to the effective potential is canceled by contributions from additional vector-like quarks, and the cutoff can naturally be higher than in the minimal Standard Model. Unlike the Little Higgs models, the cutoff sensitivity from one loop gauge contributions is not canceled. However, such gauge contributions are naturally small as long as the cutoff is below 6 TeV. Precision electroweak corrections are suppressed relative to those of Technicolor or generic Little Higgs theories. In some versions of the intermediate scenario, the Higgs mass is computable in terms of the masses of these additional fermions and the Nambu-Goldstone Boson decay constant. In addition to the Higgs, new scalar and pseudoscalar particles are typically present at the weak scale.

hep-ph↗
arXiv2003

Supersymmetry on a Spatial Lattice

We construct a variety of supersymmetric gauge theories on a spatial lattice, including N=4 supersymmetric Yang-Mills theory in 3+1 dimensions. Exact lattice supersymmetry greatly reduces or eliminates the need for fine tuning to arrive at the desired continuum limit in these examples.

hep-lat↗
arXiv2003

Supersymmetry on a Euclidean Spacetime Lattice I: A Target Theory with Four Supercharges

We formulate a Euclidean spacetime lattice whose continuum limit is (2,2) supersymmetric Yang-Mills theory in two dimensions, a theory which possesses four supercharges and an anomalous global chiral symmetry. The lattice action respects one exact supersymmetry, which allows the target theory to emerge in the continuum limit without fine-tuning. Our method exploits an orbifold construction described previously for spatial lattices in Minkowski space, and can be generalized to more complicated theories with additional supersymmetry and more spacetime dimensions.

hep-lat↗
arXiv2002

Hadron Masses and Screening from AdS Wilson Loops

We show that in strongly coupled N=4 SYM the binding energy of a heavy and a light quark is independent of the strength of the coupling constant. As a consequence we are able to show that in the presence of light quarks the analog of the QCD string can snap and color charges are screened. The resulting neutral mesons interact with each other only via pion exchange and we estimate the masses

hep-th↗
arXiv2002

Adding flavor to AdS/CFT

Coupling fundamental quarks to QCD in the dual string representation corresponds to adding the open string sector. Flavors therefore should be represented by space-time filling D-branes in the dual 5d closed string background. This requires several interesting properties of D-branes in AdS. D-branes have to be able to end in thin air in order to account for massive quarks, which only live in the UV region. They must come in distinct sets, representing the chiral global symmetry, with a bifundamental field playing the role of the chiral condensate. We show that these expectations are born out in several supersymmetric examples. To analyze most of these properties it is not necessary to go beyond the probe limit in which one neglects the backreaction of the flavor D-branes.

hep-th↗
arXiv2002

Absence of a VVDZ Discontinuity in AdS_AdS

We clarify the role of gauge invariance for the theory of an AdS4 brane embedded in AdS5. The presence of a nonvanishing mass parameter even for the lightest KK mode of the graviton indicates that all of the spin-2 modes propagate five polarization states. Despite this fact, it was shown earlier that the classical theory has a smooth limit as the mass parameter is taken to zero. We argue that locality in the fifth dimension ensures that this property survives at the quantum level.

hep-th↗
arXiv2000

Effective theories and black hole production in warped compactifications

We investigate aspects of the four-dimensional effective description of brane world scenarios based on warped compactification on anti-de Sitter space. The low-energy dynamics is described by visible matter gravitationally coupled to a ``dark'' conformal field theory. We give the linearized description of the 4d stress tensor corresponding to an arbitrary 5d matter distribution. In particular a 5d falling particle corresponds to a 4d expanding shell, giving a 4d interpretation of a trajectory that misses a black hole only by moving in the fifth dimension. Breakdown of the effective description occurs when either five-dimensional physics or strong gravity becomes important. In scenarios with a TeV brane, the latter can happen through production of black holes near the TeV scale. This could provide an interesting experimental window on quantum black hole dynamics.

hep-th↗
arXiv1999

Mirror symmetry for N=1 QED in three dimensions

We construct three-dimensional N=1 QED with N_f flavors using branes of type IIB string theory. This theory has a mirror, which can be realized using the S-dual brane configuration. As in examples with more supersymmetry, the Higgs branch of the original theory gets mapped into the Coulomb branch of the mirror. We use parity invariance to argue that these branches cannot be lifted by quantum corrections.

hep-th↗
arXiv1999

Five-branes, Seven-branes and Five-dimensional E_n field theories

We generalize the (p,q) 5-brane web construction of five-dimensional field theories by introducing (p,q) 7-branes, and apply this construction to theories with a one-dimensional Coulomb branch. The 7-branes render the exceptional global symmetry of these theories manifest. Additionally, 7-branes allow the construction of all E_n theories up to n=8, previously not possible in 5-brane configurations. The exceptional global symmetry in the field theory is a subalgebra of an affine symmetry on the 7-branes, which is necessary for the existence of the system. We explicitly determine the quantum numbers of the BPS states of all E_n theories using two simple geometrical constraints.

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