2,115 research outputs found
Search for Low Mass Higgs at the Tevatron
We present CDF and D0 searches for a Standard Model Higgs boson produced
associatively with a W or Z boson at sqrt{s}=1.96 TeV using up to 1 fb^-1 of
analyzed Tevatron data collected from February 2002 to February 2006. For Higgs
masses less than 135 GeV/c^2, as is favored by experimental and theoretical
constraints, WH->lnubb, ZH->llbb, and ZH->nunubb are the most sensitive decay
channels to search for the Higgs boson. Both CDF and D0 have analyzed these
three channels and found no evidence for Higgs production, and therefore set
upper limits on the Higgs production cross-section. While the analyses are not
yet sensitive to Standard Model Higgs production, improvements in analysis
techniques are increasing sensitivity to the Higgs much faster than added
luminosity alone.Comment: ICHEP Moscow 2006 proceeding
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Searches for the standard model Higgs at the Tevatron
The CDF and D0 experiments at the Tevatron are currently the only capable of searching for the Standard Model Higgs boson. This article describes their most sensitive searches in the expected Higgs mass range, focusing on advanced methods used to extract the maximal sensitivity from the data. CDF presents newly updated results for H {yields} W{sup +}W{sup -} and Zh {yields} l{sup +}l{sup -}b{bar b}. D0 presents two new searches for WH {yields} lvb{bar b}. These new analyses use the same 1 fb{sup -1} dataset as previous searches, but with improved techniques resulting in markedly improved sensitivity
High-precision measurement of the W boson mass with the CDF II detector
The mass of the W boson, a mediator of the weak force between elementary particles, is tightly constrained by the symmetries of the standard model of particle physics. The Higgs boson was the last missing component of the model. After observation of the Higgs boson, a measurement of the W boson mass provides a stringent test of the model. We measure the W boson mass, MW, using data corresponding to 8.8 inverse femtobarns of integrated luminosity collected in proton-antiproton collisions at a 1.96 tera-electron volt center-of-mass energy with the CDF II detector at the Fermilab Tevatron collider. A sample of approximately 4 million W boson candidates is used to obtain [Formula: see text], the precision of which exceeds that of all previous measurements combined (stat, statistical uncertainty; syst, systematic uncertainty; MeV, mega-electron volts; c, speed of light in a vacuum). This measurement is in significant tension with the standard model expectation
Search for coherent elastic neutrino-nucleus scattering at a nuclear reactor with CONNIE 2019 data
The Coherent Neutrino-Nucleus Interaction Experiment (CONNIE) is taking data at the Angra 2 nuclear reactor with the aim of detecting the coherent elastic scattering of reactor antineutrinos with silicon nuclei using charge-coupled devices (CCDs). In 2019 the experiment operated with a hardware binning applied to the readout stage, leading to lower levels of readout noise and improving the detection threshold down to 50 eV. The results of the analysis of 2019 data are reported here, corresponding to the detector array of 8 CCDs with a fiducial mass of 36.2 g and a total exposure of 2.2 kg-days. The difference between the reactor-on and reactor-off spectra shows no excess at low energies and yields upper limits at 95% confidence level for the neutrino interaction rates. In the lowest-energy range, 50 − 180 eV, the expected limit stands at 34 (39) times the standard model prediction, while the observed limit is 66 (75) times the standard model prediction with Sarkis (Chavarria) quenching factors
Precision measurement of Compton scattering in silicon with a skipper CCD for dark matter detection
Experiments aiming to directly detect dark matter through particle recoils can achieve energy thresholds of O(10 eV). In this regime, ionization signals from small-angle Compton scatters of environmental γ rays constitute a significant background. Monte Carlo simulations used to build background models have not been experimentally validated at these low energies. We report a precision measurement of Compton scattering on silicon atomic shell electrons down to 23 eV. A skipper charge-coupled device with single-electron resolution, developed for the DAMIC-M experiment, was exposed to a 241Am γ-ray source over several months. Features associated with the silicon K-, L1-, and L2,3-shells are clearly identified, and scattering on valence electrons is detected for the first time below 100 eV. We find that the relativistic impulse approximation for Compton scattering, which is implemented in Monte Carlo simulations commonly used by direct detection experiments, does not reproduce the measured spectrum below 0.5 keV. The data are in better agreement with ab initio calculations originally developed for x-ray absorption spectroscopy
Characterization of the background spectrum in DAMIC at SNOLAB
We construct the first comprehensive radioactive background model for a dark matter search with charge-coupled devices (CCDs). We leverage the well-characterized depth and energy resolution of the DAMIC at SNOLAB detector and a detailed geant4-based particle-transport simulation to model both bulk and surface backgrounds from natural radioactivity down to 50 eVee. We fit to the energy and depth distributions of the observed ionization events to differentiate and constrain possible background sources, for example, bulk 3H from silicon cosmogenic activation and surface 210Pb from radon plate-out. We observe the bulk background rate of the DAMIC at SNOLAB CCDs to be as low as 3.1±0.6 counts kg−1 day−1 keV−1ee, making it the most sensitive silicon dark matter detector. Finally, we discuss the properties of a statistically significant excess of events over the background model with energies below 200 eVee
Characterization of timing and spacial resolution of novel TI-LGAD structures before and after irradiation
The characterization of spacial and timing resolution of the novel Trench Isolated LGAD (TI-LGAD) technology is presented. This technology has been developed at FBK with the goal of achieving 4D pixels, where an accurate position resolution is combined in a single device with the precise timing determination for Minimum Ionizing Particles (MIPs). In the TI-LGAD technology, the pixelated LGAD pads are separated by physical trenches etched in the silicon. This technology can reduce the interpixel dead area, mitigating the fill factor problem. The TI-RD50 production studied in this work is the first one of pixelated TI-LGADs. The characterization was performed using a scanning TCT setup with an infrared laser and a Sr source setup
DAMIC at SNOLAB
We introduce the fully-depleted charge-coupled device (CCD) as a particle
detector. We demonstrate its low energy threshold operation, capable of
detecting ionizing energy depositions in a single pixel down to 50 eVee. We
present results of energy calibrations from 0.3 keVee to 60 keVee, showing that
the CCD is a fully active detector with uniform energy response throughout the
silicon target, good resolution (Fano ~0.16), and remarkable linear response to
electron energy depositions. We show the capability of the CCD to localize the
depth of particle interactions within the silicon target. We discuss the mode
of operation and unique imaging capabilities of the CCD, and how they may be
exploited to characterize and suppress backgrounds. We present the first
results from the deployment of 250 um thick CCDs in SNOLAB, a prototype for the
upcoming DAMIC100. DAMIC100 will have a target mass of 0.1 kg and should be
able to directly test the CDMS-Si signal within a year of operation.Comment: 13 pages, 12 figures, proceedings prepared for 13th International
Conference on Topics in Astroparticle and Underground Physics (TAUP2013
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