Search results for "coupling [Lambda(1520)]"
showing 10 items of 501 documents
Light-by-light forward scattering sum rules for charmonium states
2017
We apply three forward light-by-light scattering sum rules to charmonium states. We show that these sum rules imply a cancellation between charmonium bound state contributions, which are mostly known from the $\gamma \gamma$ decay widths of these states, and continuum contributions above $D \bar D$ threshold, for which we provide a duality estimate. We also show that two of these sum rules allow to predict the yet unmeasured $\gamma^\ast \gamma$ coupling of the $\chi_{c1}(1P)$ state, which can be tested at present high-luminosity $e^+ e^-$ colliders.
Λb→J/ψK0Λreaction and a hidden-charm pentaquark state with strangeness
2016
We study the Lambda(b) -> J/psi K-0 Lambda reaction considering both the K-0 Lambda interaction with its coupled channels and the J/psi Lambda interaction. The latter is described by taking into account the fact that there are predictions for a hidden-charm state with strangeness that couples to J/psi Lambda By using the coupling of the resonance to J/psi Lambda from these predictions, we show that a neat peak can be observed in the J/psi Lambda invariant mass distribution, rather stable under changes of unknown magnitudes. In some cases, one finds a dip structure associated to that state, but a signal of the state shows up in the J/psi Lambda spectrum.
Search for the Production of Narrowtb¯Resonances in1.9 fb−1ofpp¯Collisions ats=1.96 TeV
2009
We present new limits on resonant tb production in ppbar collisions at sqrt(s) = 1.96 TeV, using 1.9 fb{sup -1} of data recorded with the CDF II detector at the Fermilab Tevatron. We reconstruct a putative tb mass in events with a lepton, neutrino candidate, and two or three jets, and search for anomalous tb production as modeled by W{prime} {yields} tb. We set a new limit on a right-handed W{prime} with standard model-like coupling, excluding any mass below 800 GeV at 95% C.L. For any narrow W{prime}-like state with mass above 800 GeV, the cross-section is found to be less than 0.28 pb at 95% C.L. We also present an exclusion of the W{prime} coupling strength versus W{prime} mass.
Ultralight dark photon as a model for early universe dark matter
2019
Dark photon is a massive vector field which interacts only with the physical photon through the kinetic mixing. This coupling is assumed to be weak so that the dark photon becomes almost unobservable in processes with elementary particles, but can serve as a dark matter particle. We argue that in very early Universe ($z>3000$) this vector field may have the equation of state of radiation ($w=1/3$) but later behaves as cold dark matter ($w=0$). This may slightly change the expansion rate of the Universe at early time and reduce the value of the sound horizon of baryon acoustic oscillations (standard ruler). As a result, in this model the value of the Hubble constant appears to be larger than…
Nonminimal dark sector physics and cosmological tensions
2019
We explore whether non-standard dark sector physics might be required to solve the existing cosmological tensions. The properties we consider in combination are an interaction between the dark matter and dark energy components, and a dark energy equation of state $w$ different from that of the canonical cosmological constant $w=-1$. In principle, these two parameters are independent. In practice, to avoid early-time, superhorizon instabilities, their allowed parameter spaces are correlated. We analyze three classes of extended interacting dark energy models in light of the 2019 Planck CMB results and Cepheid-calibrated local distance ladder $H_0$ measurements of Riess et al. (R19), as well …
Dynamical Dark sectors and Neutrino masses and abundances
2020
We investigate generalized interacting dark matter-dark energy scenarios with a time-dependent coupling parameter, allowing also for freedom in the neutrino sector. The models are tested in the phantom and quintessence regimes, characterized by an equation of state $w_x-1$, respectively. Our analyses show that for some of the scenarios the existing tensions on the Hubble constant $H_0$ and on the clustering parameter $S_8$ can be significantly alleviated. The relief is either due to \textit{(a)} a dark energy component which lies within the phantom region; or \textit{(b)} the presence of a dynamical coupling in quintessence scenarios. The inclusion of massive neutrinos into the interaction …
Yukawa coupling corrections to the decay $H^+ \to W^+ A^0$
1998
We compute the fermionic radiative contributions to the decay $H^+ \to W^{+(*)} A^0$ in the framework of models with two Higgs doublets (2HDM), for the case of an on-shell and off-shell W. We show that, in the majority of the cases, current measurements of the $\rho$ parameter suggest $M_{H^{\pm}}\ge M_A$ and such decays could invalidate current charged Higgs searches or aid detection in the region $M_{H^{\pm}}\approx M_W$. We find that the radiative corrections may approach 50% for small values of $\tan\beta$.
Search for axionlike dark matter with a liquid-state nuclear spin comagnetometer
2019
Physical review letters 122(19), 191302 (2019). doi:10.1103/PhysRevLett.122.191302
Evidence for the two pole structure of the Lambda(1405) resonance
2005
The K^- p --> pi^0 pi^0 Sigma^0 reaction is studied within a chiral unitary model. The distribution of pi^0 Sigma^0 states forming the Lambda(1405) shows, in agreement with a recent experiment, a peak at 1420 MeV and a relatively narrow width of Gamma = 38 MeV. The mechanism for the reaction is largely dominated by the emission of a pi^0 prior to the K^- p interaction leading to the Lambda(1405). This ensures the coupling of the Lambda(1405) to the K^- p channel, thus maximizing the contribution of the second state found in chiral unitary theories, which is narrow and of higher energy than the nominal Lambda(1405). This is unlike the pi^- p --> K^0 ��Sigma reaction, which gives more w…
Discovering the h→Zγ decay in tt¯ associated production
2020
We explore the prospects to discover the $h \to Z \gamma$ decay in $t\bar t$-associated production, featuring a signal-to-background ratio of ${\cal O}(1)$. Performing a detailed analysis of the semi-leptonic $t \bar t $-decay channel, we demonstrate that the production mode could lead to a $\sim5\,\sigma$ discovery at the high-luminosity LHC, while the effective $h Z \gamma$ coupling could be extracted with a $\sim15\,\%$ accuracy. Extending the analysis to potential future $pp$ colliders with 27 TeV and 100 TeV center-of-mass energies, we also show that the latter would allow precision measurements at the few percent level, rendering possible precise extractions of the spin and CP propert…