89608693
Limits on four-top-quark production from the ATLAS same-sign top-quark search
We repurpose the recent ATLAS search for same-sign top quarks in data with $1.0\text{ }\text{ }{\mathrm{fb}}^{\ensuremath{-}1}$ in the context of a search for production of four top quarks. Using the null results of that search, we place limits on the four-top-quark production cross section of about 1 pb. These limits are larger than the expected standard model rate for four-top-quark production, but are already strong enough to place interesting constraints on models which enhance that rate. We interpret these results in the context of models in which the right-handed top quark is composite and find limits on the compositeness scale of about 700 GeV.
117824663
Search for Randall -Sundrum gravitons in dielectron and diphoton final states with 5.4 fb-1 of DO data
A search for the lightest Kaluza-Klein mode of the graviton in the Randall-Sundrum model with a warped extra dimension is performed in the dielectron and diphoton channels. The data set used for the search corresponds to 5.4 fb{sup -1} of data from p{bar p} collisions at a center-of-mass energy of 1.96 TeV, collected with the D0 detector at the Fermilab Tevatron between July 2002 and Summer 2009. We search for resonances in the invariant mass spectrum of two electromagnetic showers from the decay of the graviton to either electron-positron pairs or photon pairs. To optimize the sensitivity, the dielectron and diphoton channels are analyzed separately, then the results are combined together in the end. We also investigate whether, due to the unique spin-2 nature of the graviton, the angular distribution of the final state particles can be used to significantly enhance the sensitivity of the search. We set 95% confidence level upper limits on the graviton production cross section times branching fraction into electron-positron pairs of between {approx} 7 fb and {approx} 0.5 fb for a range of graviton masses from 220 GeV and 1050 GeV, respectively. Compared with Randall-Sundrum model predictions, these results correspond to lower limits on themore » lightest graviton mass between 440 GeV and 1040 GeV, for the dimensionless graviton coupling to the Standard Model fields k/{bar M}{sub Pl} in the range from 0.01 to 0.1. In addition, for coupling k/{bar M}{sub Pl} of 0.01, gravitons with masses between 460 GeV and 560 GeV are also excluded at 95% confidence level. These results represent the most sensitive limits to date.« less
53526303
Mono-everything: Combined limits on dark matter production at colliders from multiple final states
Searches for dark matter production at particle colliders are complementary to direct-detection and indirect-detection experiments and especially powerful for small masses, mχ<100  GeV. An important collider dark matter signature is due to the production of a pair of these invisible particles with the initial-state radiation of a standard model particle. Currently, collider searches use individual and nearly orthogonal final states to search for initial-state jets, photons or massive gauge bosons. We combine these results across final states and across experiments to give the strongest current collider-based limits in the context of effective field theories and map these to limits on dark matter interactions with nuclei and to dark matter self-annhiliation.
32140684
Structure of the MTIP-MyoA complex, a key component of the malaria parasite invasion motor.
The causative agents of malaria have developed a sophisticated machinery for entering multiple cell types in the human and insect hosts. In this machinery, a critical interaction occurs between the unusual myosin motor MyoA and the MyoA-tail Interacting Protein (MTIP). Here we present one crystal structure that shows three different conformations of Plasmodium MTIP, one of these in complex with the MyoA-tail, which reveal major conformational changes in the C-terminal domain of MTIP upon binding the MyoA-tail helix, thereby creating several hydrophobic pockets in MTIP that are the recipients of key hydrophobic side chains of MyoA. Because we also show that the MyoA helix is able to block parasite growth, this provides avenues for designing antimalarials.
119006950
Recent $J / \psi$ results from BES II
Multiquark searches have been a hot topic in recent years. Some threshold enhancements were observed during the analysis of 58M $\jpsi$ events collected by BES II detector. These enhancements can't be explained by the standard model and may be candidates of multiquark. BES also contribute a lot to the study of light scalar mesons, such as $\sigma$,$\kappa$,$f_{0}(1370)$ and $f_{0}(1710)$ etc. Study of the excited baryon states and measurements of some $\jpsi$ decays are also done with the $\jpsi$ events of BES.