ATLAS SM VH(bb) Run-2 Search

The Higgs boson discovered at the LHC in 2012 has been observed coupling directly to $W$ and $Z$ bosons and to $\tau$ leptons, and indirectly to top quarks. In order to probe whether it is indeed the particle predicted by the Standard Model, direct couplings of the Higgs boson to quarks must also be measured. The Higgs boson decays most often to a pair of bottom quarks (with a branching ratio of 58%). When the Higgs boson is produced alone in gluon-gluon fusion, the signal in this decay mode is overwhelmed by the regular multi-jet background. By requiring the Higgs boson to be produced in association with a vector boson $V$ ($W$ or $Z$), which is further required to decay leptonically, data events can be selected using charged-lepton or missing transverse energy triggers. The Tevatron experiments presented combined results showing evidence for the $VH(b\bar{b})$ process at a significance level of about 3 standard deviations, while the combined LHC results from Run-1 data show a 2.6 standard deviation evidence for the $H\rightarrow b\bar{b}$ decay mode. In this poster, the ATLAS $VH(b\bar{b})$ search using Run-2 data is summarised.Comment: 4 pages, 4 figures, Proceedings for the 38th International Conference on High Energy Physics, Chicago, IL, USA, 03 - 10 Aug 2016, http://cds.cern.ch/record/223160

Combined upper limit on Standard Model Higgs boson production at CDF

The Higgs boson is the only elementary particle predicted by the Standard Model (SM) that has neither been confirmed nor refuted. The CDF collaboration has performed SM Higgs searches in many channels using p\pbar collisions at a centre-of-mass energy \sqrt{s}=1.96\tev. We present the latest combined Higgs boson search at CDF. Since the previous year's combination, the sensitivity is increased through the addition of new channels, the improvement of existing channels and the addition of new data samples. We also use the latest parton distribution functions and $gg \rightarrow H$ theoretical cross sections when modelling the signal event yields. Using integrated luminosities of up to 8.2 \invfb, we observe a good agreement between data and the background prediction. Since we do not see a Higgs boson excess, we set 95% CL upper limits on the Higgs boson cross section in the range between 100 and 200 \gevcc, with 5 \gevcc increments. The observed (expected) limits for a 115 and a 165 \gevcc Higgs boson are 1.55 (1.49) and 0.75 (0.79) $\times$ SM, respectively. Since last year, the Higgs boson excluded range by CDF is extended to 156.5 - 173.7 and 100 - 104.5 \gevcc.Comment: 4 pages, 5 figures, proceeding for the EPS 2011 CDF Standard Model Higgs Combination, accepted for publication in the journal Proceedings of Scienc

Search for the Standard Model Higgs Boson Produced in Association with a WW Boson in the Isolated-Track Charged-Lepton Channel Using the Collider Detector at Fermilab

This dissertation presents an experimental search for the Standard Model Higgs boson produced in association to the W boson in proton antiproton collisions at a center of mass energy of 1.96 TeV and recorded with the Collider Detector at Fermilab. We improve the sensitivity of the WH search by 17% through increased signal yield by 33% by introducing a novel method to reconstruct charged lepton candidates based on an isolated track, as well as a novel method to combine triggers in order to maximize the signal yield and yet not use an OR between triggers. The observed (median expected) 95% confidence level SM Higgs upper limits on cross section times branching ratio vary between 2.39 x SM (2.73 x SM) for a Higgs mass of 100 GeV/c^2 to 31.1 x SM (31.2 x SM) for a Higgs mass of 150 GeV/c^2, while the value for a 115 GeV/c^2 Higgs boson is that of 5.08 x SM (3.79 x SM).Comment: thesis, 208 page

A Novel in situ Trigger Combination Method

Searches for rare physics processes using particle detectors in high-luminosity colliding hadronic beam environments require the use of multi-level trigger systems to reject colossal background rates in real time. In analyses like the search for the Higgs boson, there is a need to maximize the signal acceptance by combining multiple different trigger chains when forming the offline data sample. In such statistically limited searches, datasets are often amassed over periods of several years, during which the trigger characteristics evolve and system performance can vary significantly. Reliable production cross-section measurements and upper limits must take into account a detailed understanding of the effective trigger inefficiency for every selected candidate event. We present as an example the complex situation of three trigger chains, based on missing energy and jet energy, that were combined in the context of the search for the Higgs (H) boson produced in association with a $W$ boson at the Collider Detector at Fermilab (CDF). We briefly review the existing techniques for combining triggers, namely the inclusion, division, and exclusion methods. We introduce and describe a novel fourth in situ method whereby, for each candidate event, only the trigger chain with the highest a priori probability of selecting the event is considered. We compare the inclusion and novel in situ methods for signal event yields in the CDF $WH$ search. This new combination method, by virtue of its scalability to large numbers of differing trigger chains and insensitivity to correlations between triggers, will benefit future long-running collider experiments, including those currently operating on the Large Hadron Collider.Comment: 17 pages, 2 figures, 6 tables, accepted by Nuclear Instruments and Methods in Physics Research

A COMPARATIVE ANALYZE OF WILLOW SHORT ROTATION COPPICE BIOMASS IN DIFFERENT SITES FROM THE WEST OF ROMANIA

Willows are trees and shrubs species important for their wood and wood products but also for their role in environmental protection. In the context of energy crises, woody biomass for short rotation coppice could be one of important energy resource. Willows hybrids RO-892, RO-1077 and RO–1082 developed by National Institute for Research and Development in Forestrywere used to establish short rotation coppice on different sites, even marginal areas like saline soil or ash pods. Biometric characteristics, diameter at 1.0 m, and the maximum height of each shoot, and also the number of shoots per stool were evaluated and the biomass potential was estimated. The research highlighted the capacity of willow to grow on difficult site conditions like saline soil or ash pods. The yield production was significantly lower than on agricultural land but th

INTERSPECIFIC VARIABILITY OF SOME ACCESSIONS OF SALIX SP. COLLECTED FROM OLTENIA REGION, ROMANIA

The Salix genus includes many species with various uses: wood production, biomass, animal feed, source of salicylic acid, land reclamation, biofuel, a.o. In order to establish a collection of potential genitors, source of resistance genes to various stressors, 39 accessions were collected in 2015 from Banat and Oltenia, Romania. This paper presents an evaluation of 20 accessions, belonging to 7 species, collected from polluted or degraded lands in Oltenia. The intra- and interspecific variability, analyzed through the prism of the production characters for SRC, is significant. The study gives the possibility of selecting some valuable genitors, for a breeding strategy and creation of new forms more adapted to the new environmental challenges. The best results regarding biomass production, sprouting capacity and growth rate were recorded by some accessions, belonging to the species S. triandra, S. viminalis, S. fragilis

Combined Forward-Backward Asymmetry Measurements in Top-Antitop Quark Production at the Tevatron

The CDF and D0 experiments at the Fermilab Tevatron have measured the asymmetry between yields of forward- and backward-produced top and antitop quarks based on their rapidity difference and the asymmetry between their decay leptons. These measurements use the full data sets collected in proton-antiproton collisions at a center-of-mass energy of $\sqrt s =1.96$ TeV. We report the results of combinations of the inclusive asymmetries and their differential dependencies on relevant kinematic quantities. The combined inclusive asymmetry is $A_{\mathrm{FB}}^{t\bar{t}} = 0.128 \pm 0.025$. The combined inclusive and differential asymmetries are consistent with recent standard model predictions

Search for dark matter produced in association with bottom or top quarks in √s = 13 TeV pp collisions with the ATLAS detector

A search for weakly interacting massive particle dark matter produced in association with bottom or top quarks is presented. Final states containing third-generation quarks and miss- ing transverse momentum are considered. The analysis uses 36.1 fb−1 of proton–proton collision data recorded by the ATLAS experiment at √s = 13 TeV in 2015 and 2016. No significant excess of events above the estimated backgrounds is observed. The results are in- terpreted in the framework of simplified models of spin-0 dark-matter mediators. For colour- neutral spin-0 mediators produced in association with top quarks and decaying into a pair of dark-matter particles, mediator masses below 50 GeV are excluded assuming a dark-matter candidate mass of 1 GeV and unitary couplings. For scalar and pseudoscalar mediators produced in association with bottom quarks, the search sets limits on the production cross- section of 300 times the predicted rate for mediators with masses between 10 and 50 GeV and assuming a dark-matter mass of 1 GeV and unitary coupling. Constraints on colour- charged scalar simplified models are also presented. Assuming a dark-matter particle mass of 35 GeV, mediator particles with mass below 1.1 TeV are excluded for couplings yielding a dark-matter relic density consistent with measurements