Search results for "sigma"
showing 10 items of 346 documents
New determination of the N-Δ(1232) axial form factors from weak pion production and coherent pion production off nuclei at T2K and MiniBooNE energies…
2010
We re-evaluate our model predictions in Phys. Rev. D 79, 013002 (2009) for different observables in neutrino induced coherent pion production. This comes as a result of the new improved fit to old bubble chamber data of the dominant axial C_5^A nucleon-to-Delta form factor. We find an increase of 20%-30% in the values for the total cross sections. Uncertainties induced by the errors in the determination of C_5^A are computed. Our new results turn out to be compatible within about $1\sigma$ with the former ones. We also stress the existing tension between the recent experimental determination of the \sigma(CC coh \pi^+)}/\sigma(NC coh \pi^0)} $ ratio by the SciBooNE Collaboration and the the…
Search for the standard model Higgs boson produced in association with a vector boson and decaying into a tau pair inppcollisions ats=8 TeVwith the …
2016
A search for the standard model Higgs boson produced in association with a vector boson with the decay H -> tau tau is presented. The data correspond to 20.3 fb(-1) of integrated luminosity from proton-proton collisions at root s = 8 TeV recorded by the ATLAS experiment at the LHC during 2012. The data agree with the background expectation, and 95% confidence-level upper limits are placed on the cross section of this process. The observed (expected) limit, expressed in terms of the signal strength mu= sigma/sigma(SM) for m(H) = 125 GeV, is mu < 5.6 (3.7). The measured value of the signal strength is mu = 2.3 +/- 1.6.
Search for the Higgs Boson inH→WW(*)Decays inpp¯Collisions ats=1.96 TeV
2006
We present a search for the standard model Higgs boson in H --> WW(*) decays with e+e-, e+/-mu-/+, and mu+mu- final states in pp collisions at a center-of-mass energy of square root of s = 1.96 TeV. The data, collected from April 2002 to June 2004 with the D0 detector, correspond to an integrated luminosity of 300-325 pb(-1), depending on the final state. The number of events observed is consistent with the expectation from backgrounds. Limits from the combination of all three channels on the Higgs boson production cross section times branching ratio sigma x BR(H --> WW(*) are presented.
Observation of the Singly Cabibbo-Suppressed DecayD+→ωπ+and Evidence forD0→ωπ0
2016
Based on 2.93 fb(-1) e(+)e(-) collision data taken at center-of-mass energy of 3.773 GeV by the BESIII detector, we report searches for the singly Cabibbo-suppressed decays D+ -> omega pi(+) and D-0 -> omega pi(0). A double tag technique is used to measure the absolute branching fractions B(D+ -> omega pi(+)) = (2.79 +/- 0.57 +/- 0.16) x 10(-4) and B(D-0 +/- omega pi(0)) = (1.17 +/- 0.34 +/- 0.07) x 10(-4), with statistical significances of 5.5 sigma and 4.1 sigma, where the first and second uncertainties are statistical and systematic, respectively.
Measurement of the Polarization of theΥ(1S)andΥ(2S)States inpp¯Collisions ats=1.96 TeV
2008
We present a study of the polarization of the $\Upsilon(1S)$ and $\Upsilon(2S)$ states using a $1.3 $ fb$^{-1}$ data sample collected by the D0 experiment in 2002--2006 during Run II of the Fermilab Tevatron Collider. We measure the polarization parameter $\alpha=(\sigma_{T}-2\sigma_{L})/(\sigma_{T}+2\sigma_{L})$, where $\sigma_{T}$ and $\sigma_{L}$ are the transversely and longitudinally polarized components of the production cross section, as a function of the transverse momentum ($p_{T}^{\Upsilon}$) for the $\Upsilon(1S)$ and $\Upsilon(2S)$. Significant $p_{T}^{\Upsilon}$-dependent longitudinal polarization is observed for the $\Upsilon(1S)$. A comparison with theoretical models is prese…
Chiral dynamics of baryon resonances and hadrons in a nuclear medium
2005
In these lectures I make an introduction to chiral unitary theory applied to the meson baryon interaction and show how several well known resonances are dynamically generated, and others are predicted. Two very recent experiments are analyzed, one of them showing the existence of two $\Lambda(1405)$ states and the other one providing support for the $\Lambda(1520)$ resonance as a quasibound state of $\Sigma(1385) \pi$. The use of chiral Lagrangians to account for the hadronic interaction at the elementary level introduces a new approach to deal with the modification of meson and baryon properties in a nuclear medium. Examples of it for $\bar{K}$, $\eta$ and $\phi$ modification in the nuclea…
Recent Developments in Chiral Dynamics of Hadrons and Hadrons in Nuclei
2007
In this talk I present recent developments in the field of hadronic physics and hadrons in the nuclear medium. I review the unitary chiral approach to meson baryon interaction and address the topics of the two dynamically generated $\Lambda(1405)$ resonances, with experiments testing it, the $\Lambda(1520)$ and $\Delta(1700)$ resonances, plus the $\Lambda(1520)$, $\Sigma(1385)$ and $\omega$ in the nuclear medium.
Triangle mechanisms in the build up and decay of the N*(1875)
2017
We have studied the $N^*(1875) (3/2^-)$ resonance with a multichannel unitary scheme, considering the $\Delta \pi$ and $\Sigma^* K$, with their interaction extracted from chiral Lagrangians, and then have added two more channels, the $N^*(1535) \pi$ and $N \sigma$, which proceed via triangle diagrams involving the $\Sigma^* K$ and $\Delta \pi$ respectively in the intermediate states. The triangle diagram in the $N^*(1535) \pi$ case develops a singularity at the same energy as the resonance mass. We determine the couplings of the resonance to the different channels and the partial decay widths. We find a very large decay width to $\Sigma^* K$, and also see that, due to interference with othe…
Exclusive non-leptonic charm baryon decays
1992
We present a spectator quark model calculation of the Cabibbo-enhanced non-leptonic decays of the lowest lying charm baryons Λc, Ξc and Ωc decaying into non-charm ground state baryons and mesons. We employ covariant quark model wave functions to describe the ground state baryons and mesons. They are obtained by boosting rest frame wave functions to equal velocity frames. The non-leptonic decay amplitudes are then obtained in terms of two wave function overlap parameters which we fit to the experimental data. We discuss general features of the flavour and helicity composition of the final states in the quark model approach. We emphasize thatW-exchange contributions are of crucial importance …
Neutral Pion Threshold Production atQ2=0.05GeV2/c2and Chiral Perturbation Theory
2001
New data are presented on the $p({e,e}^{\ensuremath{'}}p){\ensuremath{\pi}}^{0}$ reaction at threshold at a four-momentum transfer of ${Q}^{2}\phantom{\rule{0ex}{0ex}}=\phantom{\rule{0ex}{0ex}}0.05{\mathrm{GeV}}^{2}{/c}^{2}$. The data were taken with the three-spectrometer setup of the A1 Collaboration at the Mainz Microtron MAMI. The complete center of mass solid angle was covered up to a center of mass energy of 4 MeV above threshold. Combined with measurements at three different values of the virtual photon polarization $\ensuremath{\epsilon}$, the structure functions ${\ensuremath{\sigma}}_{T}$, ${\ensuremath{\sigma}}_{L}$, ${\ensuremath{\sigma}}_{\mathrm{TT}}$, and ${\ensuremath{\sigma…