Search results for "matèria fosca"
showing 4 items of 4 documents
Search for a Stable Six-Quark State at BABAR
2019
Recent investigations have suggested that the six-quark combination uuddss could be a deeply bound state (S) that has eluded detection so far, and a potential dark matter candidate. We report the first search for a stable, doubly strange six-quark state in Upsilon -> S anti-Lambda anti-Lambda decays based on a sample of 90 million Upsilon(2S) and 110 million Upsilon(3S) decays collected by the BABAR experiment. No signal is observed, and 90% confidence level limits on the combined Upsilon(2S,3S) -> S anti-Lambda anti-Lambda branching fraction in the range (1.2-1.4)x10^-7 are derived for m_S < 2.05 GeV. These bounds set stringent limits on the existence of such exotic particles.
Coupled dark matter-dark energy in light of near Universe observations
2010
Cosmological analysis based on currently available observations are unable to rule out a sizeable coupling among the dark energy and dark matter fluids. We explore a variety of coupled dark matter-dark energy models, which satisfy cosmic microwave background constraints, in light of low redshift and near universe observations. We illustrate the phenomenology of different classes of dark coupling models, paying particular attention in distinguishing between effects that appear only on the expansion history and those that appear in the growth of structure. We find that while a broad class of dark coupling models are effectively models where general relativity (GR) is modified - and thus can b…
Search for a muonic dark force at BaBar
2016
Many models of physics beyond the Standard Model predict the existence of new Abelian forces with new gauge bosons mediating interactions between "dark sectors" and the Standard Model. We report a search for a dark boson Z' coupling only to the second and third generations of leptons in the reaction e+e- -> mu+mu- Z', Z' -> mu+mu- using 514 fb-1 of data collected by the BABAR experiment. No significant signal is observed for Z' masses in the range 0.212 - 10 GeV. Limits on the coupling parameter g' as low as 7x10^-4 are derived, leading to improvements in the bounds compared to those previously derived from neutrino experiments.
Phenomenological and cosmological aspects of electroweak models beyond the Standard Model
2020
El model estàndard de física de partícules (SM) és la millor teoria que tenim hui en dia per a entendre la natura. No obstant això, malgrat ser capaç de descriure amb alta precisió la major part dels fenòmens que observem, hi ha evidències de física més enllà les quals, sostingudes per observacions experimentals, denoten que el SM no pot ser la teoria final i motiva la cerca d'una teoria que el complete: -L'origen de la massa dels neutrins i la seua natura. Al Capítol 1 es descriu l'estatus dels neutrins i s'introdueix els mecanismes principals que poden generar la seua massa, la connexió entre la seua natura i el número leptònic es discuteix al Capítol 5, mentre que a aquest capítol com al…