59031368
Illuminating the 130 GeV gamma line with continuum photons
A bstractThere is evidence for a 130 GeV γ-ray line at the Galactic Center in the Fermi Large Area Telescope data. Dark matter candidates that explain this feature should also annihilate to Standard Model particles, resulting in a continuous spectrum of photons. To study this continuum, we analyze the Fermi data down to 5 GeV, restricted to the inner 3◦ of the Galaxy. We place a strong bound on the ratio of continuum photons to monochromatic line photons that is independent of uncertainties in the dark matter density profile. The derived constraints exclude neutralino dark matter as an explanation for the line.
17675959
Leptophilic dark matter from the lepton asymmetry.
We present a model of weak scale dark matter (DM) where the thermal DM density is set by the lepton asymmetry due to the presence of higher dimension lepton violating operators. In these models there is generically a separation between the annihilation cross section responsible for the relic abundance (through lepton violating operators) and the annihilation cross section that is relevant for the indirect detection of DM (through lepton preserving operators). This implies a perceived boost in the annihilation cross section in the Galaxy today relative to that derived for canonical thermal freeze-out, giving a natural explanation for the observed cosmic ray electron and positron excesses, without resorting to a Sommerfeld enhancement. These models motivate continued searches for DM with apparently nonthermal annihilation cross sections. The DM may also play a role in radiatively generating Majorana neutrino masses.
53390439
Boosting stop searches with a 100 TeV proton collider
A bstractA proton-proton collider with center of mass energy around 100 TeV is the energy frontier machine that is likely to succeed the LHC. One of the primary physics goals will be the continued exploration of weak scale naturalness. Here we focus on the pair-production of stops that decay to a top and a neutralino. Most of the heavy stop parameter space results in highly boosted tops, populating kinematic regimes inaccessible at the LHC. New strategies for boosted top-tagging are needed and a simple, detector-independent tagger can be constructed by requiring a muon inside a jet. Assuming 20% systematic uncertainties, this future collider can discover (exclude) stops with masses up to 5.5 (8) TeV with 3000 fb−1 of integrated luminosity. Studying how the exclusion limits scale with luminosity motivates going beyond this benchmark in order to saturate the discovery potential of the machine.
119221065
SUSY simplified models at 14, 33, and 100 TeV proton colliders
A bstractResults are presented for a variety of SUSY Simplified Models at the 14 TeV LHC as well as a 33 and 100 TeV proton collider. Our focus is on models whose signals are driven by colored production. We present projections of the upper limit and discovery reach in the gluino-neutralino (for both light and heavy flavor decays), squark-neutralino, and gluino-squark Simplified Model planes. Depending on the model a jets + $ E_T^{\mathrm{miss}} $, mono-jet, or same-sign di-lepton search is applied. The impact of pileup is explored. This study utilizes the Snowmass backgrounds and combined detector. Assuming 3000 fb−1 of integrated luminosity, a gluino that decays to light flavor quarks can be discovered below 2.3 TeV at the 14 TeV LHC and below 11 TeV at a 100 TeV machine.
118984899
Singlet-Doublet Dark Matter
In light of recent data from direct detection experiments and the Large Hadron Collider, we explore models of dark matter in which an SU(2){sub L} doublet is mixed with a Standard Model singlet. We impose a thermal history. If the new particles are fermions, this model is already constrained due to null results from XENON100. We comment on remaining regions of parameter space and assess prospects for future discovery. We do the same for the model where the new particles are scalars, which at present is less constrained. Much of the remaining parameter space for both models will be probed by the next generation of direct detection experiments. For the fermion model, DeepCore may also play an important role.
118615137
Correlation between the spin-independent and spin-dependent direct detection of dark matter
We study the correlation between spin-independent and spin-dependent scattering in the context of minimal supersymmetric standard model neutralino dark matter for both thermal and nonthermal histories. We explore the generality of this relationship with reference to other models. We discuss why either fine-tuning or numerical coincidences are necessary for the correlation to break down. We derive upper bounds on spin-dependent scattering mediated by a ${Z}^{0}$ boson.
18690669
Fixed-Velocity Chiral Sum Rules for Nuclear Matter
Infinite sets of sum rules involving the excitations of infinite nuclear matter are derived using only completeness, the current algebra implicit in QCD, and relativistic covariance. The sum rules can be used for isospin-asymmetric nuclear matter, including neutron matter. They relate the chiral condensate and the isospin density to weighted sums over states with fixed velocity relative to the nuclear matter ground state.
12039487
Phenomenology of the baryon resonance 70-plet at large N c
We examine the multiplet structure and decay channels of baryon resonances in the large ${N}_{c}$ QCD generalization of the ${N}_{c}=3$ SU(6) spin-flavor $\mathbf{70}$. We show that this ``$\mathbf{70}$,'' while a construct of large ${N}_{c}$ quark models, actually consists of five model-independent irreducible spin-flavor multiplets in the large ${N}_{c}$ limit. The preferred decay modes for these resonances fundamentally depend upon which of the five multiplets to which the resonance belongs. For example, there exists an SU(3) ``$\mathbf{8}$'' of resonances that is $\ensuremath{\eta}$-philic and $\ensuremath{\pi}$-phobic, and an ``$\mathbf{8}$'' that is the reverse. Moreover, resonances with a strong SU(3) ``$\mathbf{1}$'' component prefer to decay via a $\overline{K}$ rather than via a $\ensuremath{\pi}$. Remarkably, available data appears to bear out these conclusions.
115378885
Baryons in QCD(AS) at Large N(c): A Roundabout Approach
QCD AS , a variant of large N c QCD in which quarks transform under the color two-index antisymmetric representation, reduces to standard QCD at N c = 3 and provides an alternative to the usual large N c extrapolation that uses fundamental representation quarks. Previous strong plausibility arguments assert that the QCD AS baryon mass scales as N 2 c ; however, the complicated combinatoric problem associated with quarks carrying two color indices impeded a complete demonstration. We develop a diagrammatic technique to solve this problem. The key ingredient is the introduction of an effective multigluon vertex: a "traffic circle" or roundabout diagram. We show that arbitrarily complicated diagrams can be reduced to simple ones with the same leading N c scaling using this device, and that the leading contribution to baryon mass does, in fact, scale as N 2 c .
119222212
Does the empirical meson spectrum support the Hagedorn conjecture
It has long been conjectured that strong interactions give rise to a Hagedorn spectrum and theoretical arguments have been presented in support of Hagedorn spectrum in large Nc QCD. This paper discusses the extent to which the meson spectrum should be viewed as evidence for a Hagedorn spectrum and argues that data do not provide a strong evidence for the Hagedorn conjecture. The conclusion is based on three reasons. It is shown that ‘realistic’ quark models have a spectrum in which the number of mesons up to 2.3 GeV grows with mass in a very similar way to the spectrum of physical mesons up to 2.3 GeV. However, these models can be shown to not have Hagedorn spectra. It is also shown that the available data are insufficient to determine the Hagedorn temperature. The data can be described with comparable accuracy by various functional forms of the prefactor that yield radically different Hagedorn temperatures. An analysis of the behavior of the spectrum for the various parity–spin–charge conjugation–isospin channels also appears to be inconsistent with what one expects if the data were in the regime dominated by exponential behavior.
19494072
Decoupling spurious baryon states in the 1/Nc expansion of QCD
We identify spurious states in meson-baryon scattering, those that appear in QCD for N{sub c}>3 but decouple for N{sub c}=3. The key observation is that the relevant flavor SU(3) Clebsch-Gordan coefficients contain factors of 1-3/N{sub c}. We show that this method works even if SU(3) is badly broken. We also observe that resonant scattering poles lying outside naive quark-model multiplets are not necessarily large N{sub c} artifacts, and can survive via configuration mixing at N{sub c}=3.