M. Wolf

Search for Dark Matter Annihilations in the Sun with the 79-String IceCube Detector

We have performed a search for muon neutrinos from dark matter annihilation in the center of the Sun with the 79-string configuration of the IceCube neutrino telescope. For the first time, the DeepCore subarray is included in the analysis, lowering the energy threshold and extending the search to the austral summer. The 317 days of data collected between June 2010 and May 2011 are consistent with the expected background from atmospheric muons and neutrinos. Upper limits are set on the dark matter annihilation rate, with conversions to limits on spin-dependent and spin-independent scattering cross sections of weakly interacting massive particles (WIMPs) on protons, for WIMP masses in the range 20-5000u2009u2009GeV/c2. These are the most stringent spin-dependent WIMP-proton cross section limits to date above 35u2009u2009GeV/c2 for most WIMP models.

Dual superconformal symmetry from AdS5xS5 superstring integrability

We discuss 2d duality transformations in the classical AdS5 � S 5 superstring and their effect on the integrable structure. T-duality along four directions in the Poincareparametrization of AdS5 maps the bosonic part of the superstring action into itself. On the bosonic level, this duality may be understood as a symmetry of the first-order (phase space) system of equations for the coset components of the current. The associated Lax connection is invariant modulo the action of an soð2; 4Þ-automorphism. We then show that this symmetry extends to the full superstring, provided one supplements the transformation of the bosonic components of the current with a transformation on the fermionic ones. At the level of the action, this symmetry can be seen by combining the bosonic duality transformation with a similar one applied to part of the fermionic superstring coordinates. As a result, the full superstring action is mapped into itself, albeit in a different � -symmetry gauge. One implication is that the dual model has the same superconformal symmetry group as the original one, and this may be seen as a consequence of the integrability of the superstring. The invariance of the Lax connection under the duality implies a map on the full set of conserved charges that should interchange some of the Noether (local) charges with hidden (nonlocal) ones and vice versa.

Measurement of the cosmic ray energy spectrum with IceTop-73

We report on the measurement of the all particle cosmic ray energy spectrum with the IceTop air shower array in the energy range from 1.6 PeV up to 1.3 EeV. The IceTop air shower array is the surface component of the IceCube Neutrino Observatory at the geographical South Pole. The analysis was performed using IceTop in its 73 station configuration when it was 90% complete. The spectrum was derived using an iterative unfolding with shower size as an energy proxy. Corresponding authors: Bakhtiyar Ruzybayev1, Javier Gonzalez1 1 University of Delaware

Threshold Energies for Single Carbon Knockout from Polycyclic Aromatic Hydrocarbons

We have measured absolute cross sections for ultrafast (femtosecond) single-carbon knockout from polycyclic aromatic hydrocarbon (PAH) cations as functions of He–PAH center-of-mass collision energy in the 10–200 eV range. Classical molecular dynamics (MD) simulations cover this range and extend up to 105 eV. The shapes of the knockout cross sections are well-described by a simple analytical expression yielding experimental and MD threshold energies of EthExp = 32.5 ± 0.4 eV and EthMD = 41.0 ± 0.3 eV, respectively. These are the first measurements of knockout threshold energies for molecules isolated in vacuo. We further deduce semiempirical (SE) and MD displacement energies, i.e., the energy transfers to the PAH molecules at the threshold energies for knockout, of TdispSE = 23.3 ± 0.3 eV and TdispMD = 27.0 ± 0.3 eV. The semiempirical results compare favorably with measured displacement energies for graphene (Tdisp = 23.6 eV).

Failure of hydrogenation in protecting polycyclic aromatic hydrocarbons from fragmentation

A recent study of soft x-ray absorption in native and hydrogenated coronene cations, C_24H_12+m^+ m=0–7, led to the conclusion that additional hydrogen atoms protect (interstellar) polycyclic aromatic hydrocarbon (PAH) molecules from fragmentation [Reitsma et al., Phys. Rev. Lett. 113, 053002 (2014)]. The present experiment with collisions between fast (30–200 eV) He atoms and pyrene (C_16H_10+m^+, m=0, 6, and 16) and simulations without reference to the excitation method suggests the opposite. We find that the absolute carbon-backbone fragmentation cross section does not decrease but increases with the degree of hydrogenation for pyrene molecules.

PHOTO-STABILITY OF SUPER-HYDROGENATED PAHs DETERMINED BY ACTION SPECTROSCOPY EXPERIMENTS

We have investigated the photo-stability of pristine and super-hydrogenated pyrene cations C

Measuring lifetimes of Polycyclic Aromatic Hydrocarbon fragments

_{16}

Dual superconformal symmetry fromAdS5×S5superstring integrability

H

Results from Low-Energy Neutrino Searches for Dark Matter in the Galactic Center with IceCube-DeepCore

_{10+m}^+, m = 0,6, mathrm{ or } 16

Results from Low-Energy Neutrino Searches for Dark Matterin the Galactic Center with IceCube-DeepCore

) by means of gas-phase action spectroscopy. Optical absorption spectra and photo-induced dissociation mass spectra are presented. By measuring the yield of mass-selected photo-fragment ions as a function of laser pulse intensity, the number of photons (and hence the energy) needed for fragmentation of the carbon backbone was determined. Backbone fragmentation of pristine pyrene ions (C