Search results for "sigma"
showing 10 items of 346 documents
Status of a hybrid three-neutrino interpretation of neutrino data
2001
We reanalyze the non-standard interaction (NSI) solutions to the solar neutrino problem in the light of the latest solar, atmospheric and reactor neutrino data. We show that such solutions, although preferred by the solar data and consistent with the oscillation description of the atmospheric neutrino data, are ruled out by the first results of the KamLAND reactor experiment, at more than 3_sigma.
Solving the solar neutrino puzzle with KamLAND and solar data
2001
We study what will be learnt about the solar neutrino puzzle and solar neutrino oscillations once the data from the KamLAND reactor neutrino experiment (soon to become available) are combined with those from the current solar neutrino experiments. We find that, in agreement with previous estimates, if the solution to the solar neutrino puzzle falls on the LMA region, KamLAND should be able to ``pin-point'' the right solution with unprecedented accuracy after a few years of data taking. Furthermore, the light side ($\theta\pi/4$) at the 95% confidence level (CL) for most of the LMA region allowed by the current data at the 99% CL, while the addition of the KamLAND data need not improve our a…
Search for new physics inlepton+photon+Xevents with929 pb−1ofpp¯collisions ats=1.96 TeV
2007
The authors present results of a search for anomalous production of events containing a charged lepton ({ell}, either e or {mu}) and a photon ({gamma}), both with high transverse momentum, accompanied by additional signatures, X, including missing transverse energy (E{sub T}) and additional leptons and photons. We use the same kinematic selection criteria as in a previous CDF search, but with a substantially larger data set, 305 pb{sup -1}, a p{bar p} collision energy of 1.96 TeV, and the upgraded CDF II detector. We find 42 {ell}{gamma}E{sub T} events versus a standard model expectation of 37.3 {+-} 5.4 events. The level of excess observed in Run I, 16 events with an expectation of 7.6 {+-…
Overview of the electromagnetic production of strange mesons at MAMI
2013
Abstract The Mainz Microtron MAMI provides a continuous-wave unpolarized or spin-polarized electron beam with energies up to 1.6 GeV and high degrees of polarization. Electro-production of strange mesons is performed in the multi-spectrometer facility with the Kaos spectrometer for kaon detection and a high-resolution spectrometer for electron detection in plane or out of plane. Differential cross section measurements of exclusive p ( e , e ′ K + ) Λ , Σ 0 reactions at low four-momentum transfers in the nucleonʼs third resonance region have been done, followed by a measurement of the beam helicity asymmetry for p ( e → , e ′ K + ) Λ . These studies are important for the understanding of the…
Combining first KamLAND results with solar neutrino data
2002
We consider the impact of the recent KamLAND data on neutrino oscillations, the first terrestrial neutrino experiment that can probe the solar neutrino anomaly. By combining the first 145.1 days of KamLAND data with the full sample of latest solar neutrino data we find an enhanced rejection against non-LMA oscillations, allowed only at more than 4 sigma with respect to LMA. Furthermore, the new data have a strong impact in narrowing down the allowed range of Delta_m^2 inside the LMA region. In contrast, our global analysis indicates that the new data have little impact on the location of the best fit point. In particular the solar neutrino mixing remains significantly non-maximal (3 sigma).
One-Pion Charm Baryon Transitions in a Relativistic Three-Quark Model
1998
We study one-pion transitions between charm baryon states in the framework of a relativistic three-quark model. We calculate the charm baryon-pion coupling factors that govern the S-wave, P-wave and D-wave one-pion transitions from the s-wave and the lowest lying p-wave charm baryon states down to the s-wave charm baryon states. For these we obtain: g_{\Sigma_c\Lambda_c\pi}=8.88 GeV^{-1}, f_{\Lambda_{c1}\Sigma_c\pi}=0.52 and f_{\Lambda_{c1}^*\Sigma_c\pi}=21.5 GeV^{-2}. We compare our rate predictions for the one-pion transitions with experimental results.
ν¯inducedK¯production off the nucleon
2012
The charged-current antikaon production off nucleons induced by antineutrinos is studied at low and intermediate energies. We extend here our previous calculation on kaon production induced by neutrinos. We have developed a microscopic model that starts from the SU(3) chiral Lagrangians and includes background terms and the resonant mechanisms associated to the lowest lying resonance in the channel, namely, the ${\ensuremath{\Sigma}}^{*}(1385)$. Our results could be of interest for the background estimation of various neutrino oscillation experiments like MiniBooNE and SuperK. They can also be helpful for the planned $\overline{\ensuremath{\nu}}$ experiments like $\mathrm{MINER}\ensuremath{…
Constraints on Coupling Constants through Charged $\Sigma$ Photoproduction
1995
The few available data for the reactions $\gamma p \rightarrow K^{0} \Sigma^{+}$ and $\gamma n \rightarrow K^{+} \Sigma^{-}$ are compared to models developed for the processes $\gamma p \rightarrow K^{+} \Sigma^{0}$ and $\gamma p \rightarrow K^{+} \Lambda$. It is found that some of these phenomenological models overpredict the measurements by up to a factor of 100. Fitting the data for all of these reactions leads to drastically reduced Born coupling constants.
A study of strange particles produced in neutrino neutral current interactions in the NOMAD experiment
2004
Results of a detailed study of strange particle production in neutrino neutral current interactions are presented using the data from the NOMAD experiment. Integral yields of neutral strange particles (K0s, Lambda, Lambda-bar) have been measured. Decays of resonances and heavy hyperons with an identified K0s or Lambda in the final state have been analyzed. Clear signals corresponding to K* and Sigma(1385) have been observed. First results on the measurements of the Lambda polarization in neutral current interactions have been obtained.
Double pion photoproduction off nuclei - Are there effects beyond final-state interaction?
2013
Photoproduction of $\pi^{0}\pi^{0}$ and $\pi^{0}\pi^{\pm}$ pairs from nuclei has been measured over a wide mass range ($^2$H, $^{7}$Li, $^{12}$C, $^{40}$Ca, and $^{\rm nat}$Pb) for photon energies from threshold to 600 MeV. The experiments were performed at the MAMI accelerator in Mainz, using the Glasgow photon tagging spectrometer and a 4$\pi$ electromagnetic calorimeter consisting of the Crystal Ball and TAPS detectors. A shift of the pion-pion invariant mass spectra for heavy nuclei to small invariant masses has been observed for $\pi^0$ pairs but also for the mixed-charge pairs. The precise results allow for the first time a model-independent analysis of the influence of pion final-sta…