397 research outputs found
Searches for R-parity violating Supersymmetry at LEP 2
Searches for pair-production of Supersymmetric particles under the assumption that R-parity is not conserved have been performed using the data collected by ALEPH at centre-of-mass energies of 130-172 GeV. The results for a dominant R-parity violating coupling LLE, for which the observed candidate events in the data are in agreement with the SM expectation, translate into lower limits on the mass of charginos, neutralinos, sleptons, sneutrinos and squarks. We also give preliminary results on the search for charginos, sleptons and sneutrinos via a dominant LQD coupling, and discuss the implications of our results on the R-parity violating interpretations of the recently reported excess of high Q2 events at HERA, and the ALEPH four jet anomaly
Undressing the Words: Prevalence of Profanity, Misogyny, Violence, and Gender Role References in Popular Music from 2006-2016
Are degrading sexual references more prevalent than non-degrading references in music popular with adolescents? The purpose of this study was to perform a content analysis of contemporary popular music with particular attention paid to the prevalence of violent, misogynistic, profane, and/or demeaning colloquial references. Billboard magazine was used to identify the top popular songs appearing on top music charts from 2006 through 2016. Data show songs with justified violence themes were most commonly found in hip-hop music, whereas songs with unjustified message themes were most often found in Pop music. The present study suggests that pop and hip-hop/rap music, genres popular with most adolescents today, use frequent references involving profanity, violence, and misogynistic themes
Single spontaneous photon as a coherent beamsplitter for an atomic matterwave
In spontaneous emission an atom in an excited state undergoes a transition to
the ground state and emits a single photon. Associated with the emission is a
change of the atomic momentum due to photon recoil. Photon emission can be
modified close to surfaces and in cavities. For an ion, localized in front of a
mirror, coherence of the emitted resonance fluorescence has been reported. In
free space experiments demonstrated that spontaneous emission destroys motional
coherence. Here we report on motional coherence created by a single spontaneous
emission event close to a mirror surface. The coherence in the free atomic
motion is verified by atom interferometry. The photon can be regarded as a
beamsplitter for an atomic matterwave and consequently our experiment extends
the original recoiling slit Gedanken experiment by Einstein to the case where
the slit is in a robust coherent superposition of the two recoils associated
with the two paths of the quanta.Comment: main text: 5 pages, 4 figure; supplementary information: 8 pages, 1
figur
Coherent radiation from neutral molecules moving above a grating
We predict and study the quantum-electrodynamical effect of parametric
self-induced excitation of a molecule moving above the dielectric or conducting
medium with periodic grating. In this case the radiation reaction force
modulates the molecular transition frequency which results in a parametric
instability of dipole oscillations even from the level of quantum or thermal
fluctuations. The present mechanism of instability of electrically neutral
molecules is different from that of the well-known Smith-Purcell and transition
radiation in which a moving charge and its oscillating image create an
oscillating dipole.
We show that parametrically excited molecular bunches can produce an easily
detectable coherent radiation flux of up to a microwatt.Comment: 4 page
Polarons with a twist
We consider a polaron model where molecular \emph{rotations} are important.
Here, the usual hopping between neighboring sites is affected directly by the
electron-phonon interaction via a {\em twist-dependent} hopping amplitude. This
model may be of relevance for electronic transport in complex molecules and
polymers with torsional degrees of freedom, such as DNA, as well as in
molecular electronics experiments where molecular twist motion is significant.
We use a tight-binding representation and find that very different polaronic
properties are already exhibited by a two-site model -- these are due to the
nonlinearity of the restoring force of the twist excitations, and of the
electron-phonon interaction in the model. In the adiabatic regime, where
electrons move in a {\em low}-frequency field of twisting-phonons, the
effective splitting of the energy levels increases with coupling strength. The
bandwidth in a long chain shows a power-law suppression with coupling, unlike
the typical exponential dependence due to linear phonons.Comment: revtex4 source and one eps figur
Measurement of the diffractive structure function in deep inelastic scattering at HERA
This paper presents an analysis of the inclusive properties of diffractive
deep inelastic scattering events produced in interactions at HERA. The
events are characterised by a rapidity gap between the outgoing proton system
and the remaining hadronic system. Inclusive distributions are presented and
compared with Monte Carlo models for diffractive processes. The data are
consistent with models where the pomeron structure function has a hard and a
soft contribution. The diffractive structure function is measured as a function
of \xpom, the momentum fraction lost by the proton, of , the momentum
fraction of the struck quark with respect to \xpom, and of . The \xpom
dependence is consistent with the form \xpoma where
in all bins of and
. In the measured range, the diffractive structure function
approximately scales with at fixed . In an Ingelman-Schlein type
model, where commonly used pomeron flux factor normalisations are assumed, it
is found that the quarks within the pomeron do not saturate the momentum sum
rule.Comment: 36 pages, latex, 11 figures appended as uuencoded fil
Observation of hard scattering in photoproduction events with a large rapidity gap at HERA
Events with a large rapidity gap and total transverse energy greater than 5
GeV have been observed in quasi-real photoproduction at HERA with the ZEUS
detector. The distribution of these events as a function of the
centre of mass energy is consistent with diffractive scattering. For total
transverse energies above 12 GeV, the hadronic final states show predominantly
a two-jet structure with each jet having a transverse energy greater than 4
GeV. For the two-jet events, little energy flow is found outside the jets. This
observation is consistent with the hard scattering of a quasi-real photon with
a colourless object in the proton.Comment: 19 pages, latex, 4 figures appended as uuencoded fil
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