1,109 research outputs found
Lepton Flavor Violation in Z and Lepton Decays in Supersymmetric Models
The observation of charged lepton flavor non-conservation would be a clear
signature of physics beyond the Standard Model. In particular, supersymmetric
(SUSY) models introduce mixings in the sneutrino and the charged slepton
sectors which could imply flavor-changing processes at rates accessible to
upcoming experiments. In this paper we analyze the possibility to observe Z -->
lep_I lep_J in the GigaZ option of TESLA at DESY. We show that although models
with SUSY masses above the current limits could predict a branching ratio BR(Z
--> mu e) accessible to the experiment, they would imply an unobserved rate of
mu --> e gamma and thus are excluded. In models with a small mixing angle
between the first and the third (or the second and the third) slepton families
GigaZ could observe Z --> tau mu (or Z --> tau e) consistently with present
bounds on lep_J --> lep_I gamma. In contrast, if the mixing angles between the
three slepton families are large the bounds from mu --> e gamma push these
processes below the reach of GigaZ. We show that in this case the masses of the
three slepton families must be strongly degenerated (with mass differences of
order 10^{-3}). We update the limits on the slepton mass insertions
delta_{LL,RR,LR} and discuss the correlation between flavor changing and g_mu-2
in SUSY models.Comment: 23 pages, 6 figures. Version to appear in Phys. Rev.
Hyaluronic Acid Enhances Gene Delivery into the Cochlea
Abstract Cochlear gene therapy can be a new avenue for the treatment of severe hearing loss by inducing regeneration or phenotypic rescue. One necessary step to establish this therapy is the development of a safe and feasible inoculation surgery, ideally without drilling the bony cochlear wall. The round window membrane (RWM) is accessible in the middle-ear space, but viral vectors placed on this membrane do not readily cross the membrane to the cochlear tissues. In an attempt to enhance permeability of the RWM, we applied hyaluronic acid (HA), a nontoxic and biodegradable reagent, onto the RWM of guinea pigs, prior to delivering an adenovirus carrying enhanced green fluorescent protein (eGFP) reporter gene (Ad-eGFP) at the same site. We examined distribution of eGFP in the cochlea 1 week after treatment, comparing delivery of the vector via the RWM, with or without HA, to delivery by a cochleostomy into the perilymph. We found that cochlear tissue treated with HA-assisted delivery of Ad-eGFP demonstrated wider expression of transgenes in cochlear cells than did tissue treated by cochleostomy injection. HA-assisted vector delivery facilitated expression in cells lining the scala media, which are less accessible and not transduced after perilymphatic injection. We assessed auditory function by measuring auditory brainstem responses and determined that thresholds were significantly better in the ears treated with HA-assisted Ad-eGFP placement on the RWM as compared with cochleostomy. Together, these data demonstrate that HA-assisted delivery of viral vectors provides an atraumatic and clinically feasible method to introduce transgenes into cochlear cells, thereby enhancing both research methods and future clinical application.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/98453/1/hum%2E2011%2E086.pd
Electronic localization at mesoscopic length scales: different definitions of localization and contact effects in a heuristic DNA model
In this work we investigate the electronic transport along model DNA
molecules using an effective tight-binding approach that includes the backbone
on site energies. The localization length and participation number are examined
as a function of system size, energy dependence, and the contact coupling
between the leads and the DNA molecule. On one hand, the transition from an
diffusive regime to a localized regime for short systems is identified,
suggesting the necessity of a further length scale revealing the system borders
sensibility. On the other hand, we show that the lenght localization and
participation number, do not depended of system size and contact coupling in
the thermodynamic limit. Finally we discuss possible length dependent origins
for the large discrepancies among experimental results for the electronic
transport in DNA sample
Qualidade fisiológica de sementes de soja convencional e transgênica RR produzidas sob aplicação foliar de manganês
Inter-relation between soybean yield and soil compaction under degraded pasture in Brazilian Savannah
Biocontrol of seed pathogens and growth promotion of common bean seedlings by Trichoderma harzianum
Quantity and quality of soil organic matter as a sustainability index under different land uses in Eastern Amazon
Search for single top quarks in the tau+jets channel using 4.8 fb of collision data
We present the first direct search for single top quark production using tau
leptons. The search is based on 4.8 fb of integrated luminosity
collected in collisions at =1.96 TeV with the D0 detector
at the Fermilab Tevatron Collider. We select events with a final state
including an isolated tau lepton, missing transverse energy, two or three jets,
one or two of them tagged. We use a multivariate technique to discriminate
signal from background. The number of events observed in data in this final
state is consistent with the signal plus background expectation. We set in the
tau+jets channel an upper limit on the single top quark cross section of
\TauLimObs pb at the 95% C.L. This measurement allows a gain of 4% in expected
sensitivity for the observation of single top production when combining it with
electron+jets and muon+jets channels already published by the D0 collaboration
with 2.3 fb of data. We measure a combined cross section of
\SuperCombineXSall pb, which is the most precise measurement to date.Comment: 12 pages, 5 figure
Measurement of Z/gamma*+jet+X angular distributions in ppbar collisions at sqrt{s}=1.96 TeV
We present the first measurements at a hadron collider of differential cross
sections for Z+jet+X production in delta phi(Z, jet), |delta y(Z, jet)| and
|y_boost(Z, jet)|. Vector boson production in association with jets is an
excellent probe of QCD and constitutes the main background to many small cross
section processes, such as associated Higgs production. These measurements are
crucial tests of the predictions of perturbative QCD and current event
generators, which have varied success in describing the data. Using these
measurements as inputs in tuning event generators will increase the
experimental sensitivity to rare signals.Comment: Published in Physics Letters B 682 (2010), pp. 370-380. 15 pages, 6
figure
Search for the standard model Higgs boson in tau final states
We present a search for the standard model Higgs boson using hadronically
decaying tau leptons, in 1 inverse femtobarn of data collected with the D0
detector at the Fermilab Tevatron ppbar collider. We select two final states:
tau plus missing transverse energy and b jets, and tau+ tau- plus jets. These
final states are sensitive to a combination of associated W/Z boson plus Higgs
boson, vector boson fusion and gluon-gluon fusion production processes. The
observed ratio of the combined limit on the Higgs production cross section at
the 95% C.L. to the standard model expectation is 29 for a Higgs boson mass of
115 GeV.Comment: publication versio
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