Observation of the Baryonic Flavor-Changing Neutral Current Decay Lambda_b -> Lambda mu+ mu-

We report the first observation of the baryonic flavor-changing neutral current decay Lambda_b -> Lambda mu+ mu- with 24 signal events and a statistical significance of 5.8 Gaussian standard deviations. This measurement uses ppbar collisions data sample corresponding to 6.8fb-1 at sqrt{s}=1.96TeV collected by the CDF II detector at the Tevatron collider. The total and differential branching ratios for Lambda_b -> Lambda mu+ mu- are measured. We find B(Lambda_b -> Lambda mu+ mu-) = [1.73+-0.42(stat)+-0.55(syst)] x 10^{-6}. We also report the first measurement of the differential branching ratio of B_s -> phi mu+ mu- using 49 signal events. In addition, we report branching ratios for B+ -> K+ mu+ mu-, B0 -> K0 mu+ mu-, and B -> K*(892) mu+ mu- decays.Comment: 8 pages, 2 figures, 4 tables. Submitted to Phys. Rev. Let

Combined Tevatron upper limit on gg->H->W+W- and constraints on the Higgs boson mass in fourth-generation fermion models

Report number: FERMILAB-PUB-10-125-EWe combine results from searches by the CDF and D0 collaborations for a standard model Higgs boson (H) in the process gg->H->W+W- in p=pbar collisions at the Fermilab Tevatron Collider at sqrt{s}=1.96 TeV. With 4.8 fb-1 of integrated luminosity analyzed at CDF and 5.4 fb-1 at D0, the 95% Confidence Level upper limit on \sigma(gg->H) x B(H->W+W-) is 1.75 pb at m_H=120 GeV, 0.38 pb at m_H=165 GeV, and 0.83 pb at m_H=200 GeV. Assuming the presence of a fourth sequential generation of fermions with large masses, we exclude at the 95% Confidence Level a standard-model-like Higgs boson with a mass between 131 and 204 GeV.We combine results from searches by the CDF and D0 collaborations for a standard model Higgs boson (H) in the process gg→H→W+W- in pp̅ collisions at the Fermilab Tevatron Collider at √s=1.96  TeV. With 4.8  fb-1 of integrated luminosity analyzed at CDF and 5.4  fb-1 at D0, the 95% confidence level upper limit on σ(gg→H)×B(H→W+W-) is 1.75 pb at mH=120  GeV, 0.38 pb at mH=165  GeV, and 0.83 pb at mH=200  GeV. Assuming the presence of a fourth sequential generation of fermions with large masses, we exclude at the 95% confidence level a standard-model-like Higgs boson with a mass between 131 and 204 GeV.Peer reviewe

Multi-messenger observations of a binary neutron star merger

On 2017 August 17 a binary neutron star coalescence candidate (later designated GW170817) with merger time 12:41:04 UTC was observed through gravitational waves by the Advanced LIGO and Advanced Virgo detectors. The Fermi Gamma-ray Burst Monitor independently detected a gamma-ray burst (GRB 170817A) with a time delay of ~1.7 s with respect to the merger time. From the gravitational-wave signal, the source was initially localized to a sky region of 31 deg2 at a luminosity distance of 40+8-8 Mpc and with component masses consistent with neutron stars. The component masses were later measured to be in the range 0.86 to 2.26 Mo. An extensive observing campaign was launched across the electromagnetic spectrum leading to the discovery of a bright optical transient (SSS17a, now with the IAU identification of AT 2017gfo) in NGC 4993 (at ~40 Mpc) less than 11 hours after the merger by the One- Meter, Two Hemisphere (1M2H) team using the 1 m Swope Telescope. The optical transient was independently detected by multiple teams within an hour. Subsequent observations targeted the object and its environment. Early ultraviolet observations revealed a blue transient that faded within 48 hours. Optical and infrared observations showed a redward evolution over ~10 days. Following early non-detections, X-ray and radio emission were discovered at the transient’s position ~9 and ~16 days, respectively, after the merger. Both the X-ray and radio emission likely arise from a physical process that is distinct from the one that generates the UV/optical/near-infrared emission. No ultra-high-energy gamma-rays and no neutrino candidates consistent with the source were found in follow-up searches. These observations support the hypothesis that GW170817 was produced by the merger of two neutron stars in NGC4993 followed by a short gamma-ray burst (GRB 170817A) and a kilonova/macronova powered by the radioactive decay of r-process nuclei synthesized in the ejecta

Limits on Anomalous Trilinear Gauge Couplings in Z gamma Events from p(p)over-bar Collisions at root s=1.96 TeV

Using Z gamma candidate events collected by the CDF detector at the Tevatron Collider, we search for potential anomalous (non-standard-model) couplings between the Z boson and the photon. Z gamma couplings vanish at tree level and are heavily suppressed at higher orders; hence any evidence of couplings indicates new physics. Measurements are performed using data corresponding to an integrated luminosity of 4.9 fb(-1) in the Z -> nu(nu) over bar decay channel and 5: 1 fb(-1) in the Z -> l(+)l(-) (l - mu, e) decay channels. The combination of these measurements provides the most stringent limits to date on Z gamma trilinear gauge couplings. Using an energy scale of Lambda = 1.5 TeV to allow for a direct comparison with previous measurements, we find limits on the CP-conserving parameters that describe Z gamma couplings to be vertical bar h(3)(gamma,Z)vertical bar < 0.022 and vertical bar h(4)(gamma,Z)vertical bar < 0.0009. These results are consistent with standard model predictions

Episodic heterogeneous decline and recovery of coral cover in the Indian Ocean

Long-term changes in coral cover for the Caribbean and the Pacific/Southeast Asia regions (PSEA) have proven extremely useful in assessing the main drivers, magnitude and timescales of change. The one major coral reef region where such assessments have not been made is the Indian Ocean (IO). Here, we compiled coral cover survey data from across the IO into a database of similar to 2,000 surveys from 366 coral reef sites collected between 1977 and 2005. The compilation shows that the 1998 mass coral bleaching event was the single most important and widespread factor influencing the change in coral cover across the region. The trend in coral cover followed a step-type function driven by the 1998 period, which differs from findings in the Caribbean and the PSEA regions where declines have been more continuous and mostly began in the 1980s. Significant regional variation was observed, with most heterogeneity occurring during and after 1998. There was a significant relationship between cover and longitude for all periods, but the relationship became stronger in the period immediately after 1998. Before 1998, highest coral cover was observed in the central IO region, while this changed to the eastern region after 1998. Coral cover and latitude displayed a significant U-shaped relationship immediately after 1998, due to a large decrease in cover in the northern-central regions. Post-1998 coral cover was directly correlated to the impact of the disturbance; areas with the lowest mortality having the highest cover with India-Sri Lanka being an outlier due to its exceptionally high recovery. In 1998, reefs within Marine Protected Areas (MPAs) were more heavily impacted than unmanaged reefs, losing significantly greater total cover. MPA recovery was greater such that no differences were observed by 2001-2005. This study indicates that the regional patterns in coral cover distribution in the IO are driven mainly by episodic and acute environmental stress