Figure 1: The observed signal strengths (μ) and uncertainties for different Higgs boson decay channels and their combination for mH=125.36 GeV. Higgs boson signals corresponding to the same decay channel are combined together for all analyses. The best-fit values are shown by the solid vertical lines. The total ±1σ uncertainties are indicated by green shaded bands, with the individual contributions from the statistical uncertainty (top), the total (experimental and theoretical) systematic uncertainty (middle), and the theory systematic uncertainty (bottom) on the signal strength shown as horizontal error bars.
On 17 March, ATLAS presented their latest Higgs physics results at an LHC seminar at CERN from data collected during the LHC's first run. The updated results include searches for the Higgs boson in association with top quarks, measurements of the spin and parity, and improved and combined coupling measurements, all showing good compatibility with Standard Model predictions. These results are also being presented at the 50th Rencontres de Moriond ElectroWeak conference, in La Thuile, Italy, this week.
Both ATLAS and CMS have published a measured value of the mass of the Higgs boson mH using the high precision H->γγ and H->ZZ*->llll channels, with accuracies limited by the statistical uncertainty. The two collaborations have joined forces to combine these measurements and today presented a new combined value of mH = 125.09 ± 0.24 (0.21 stat. ± 0.11 syst.) GeV, the most precise measured value to date, with an uncertainty reduced as low as 2 parts in a thousand (0.2%).
Once the mass of the Higgs boson is known, the Standard Model predicts precisely the probability (cross-section, σ) for each of the different ways the Higgs boson can be produced from the collision of protons inside ATLAS, the most probable being the fusion of two gluons. The Standard Model also predicts each of the different ways the Higgs Boson can decay; for example via two Z bosons into two pairs of leptons (electron (e), muon (μ) or tau (τ) particles).
ATLAS physicists have been working hard to make precision measurements of the properties of the Higgs boson, such as its production and decay rates, and also its spin, to compare to the predictions of the Standard Model. The comparison can tell us whether the observed Higgs Boson is fully responsible for electroweak symmetry breaking, the phenomena which invoked its prediction, or whether new unknown particles or phenomena play a role in this process.
Studies of the production and decay properties of the Higgs boson were presented where the Higgs boson decays into vector bosons, (γγ, ZZ, WW, Zγ) and into fermions (ττ, bb, μμ). The signal strength μ = σ/σSM allows one to compare the measured cross-sections (σ) of each decay channel, to that predicted by the Standard Model, (σSM). All results, shown in Figure 1, were found to be compatible with μ=1, corresponding to Standard Model predictions. The new combination of all production and decay channels gives the most precise value from ATLAS to date, of μ = 1.18 +0.15 – 0.14.
Latest results were presented on the search for the production of the Higgs boson in association with two top-quarks (link to both ttH papers), a very rare process, and the only channel that allows one to directly probe the mysteriously large top-Higgs Yukawa coupling. A number of different decay modes of the Higgs boson were analysed, including decays into fermions (bb, ττ), and into bosons (WW, ZZ) the latter decay mode being measured for the first time by ATLAS in association with top quarks. Gathering all the decay channels together the data showed a small an excess of events over background with a strength μ(ttH) = 1.80 +0.84 -0.74, where μ =1 corresponds to Standard Model predictions. This gives a significance of 2.4 standard deviations with respect to a no-ttH hypothesis. To reach enough significance for the observation of the Higgs boson in this channel ATLAS will require more data collected in Run 2.
Improved studies of the spin and parity of the Higgs boson were presented, confirming that the Standard Model hypothesis, corresponding to a spin-0 particle with positive parity, is favoured at more than 99% confidence level.
The LHC will restart in just a few weeks for Run 2 with a proton-proton collision energy of 13 TeV, more than 60% higher than that of Run 1. In these conditions, the production rate of the Standard Model Higgs boson will increase by more than a factor of 2, and by almost a factor of 4 in the case of the ttH process described above. With an upgraded detector and updated software, ATLAS is ready to exploit the full potential of the LHC's second run to learn more about the Higgs boson, and to look beyond for new phenomena.What does the name brayden mean? How to clean your liver? What are polarized sunglasses? How they do it magic tricks? What does it mean if your vagina hurts? dolly how to rate helper How to do magic tricks with everyday objects? What is the meaning of propitiation in the bible? How many steps to lose weight? How long does it take for flu shot to work? How to stop ringing in ears at night? What does castrated mean? What is the meaning of hasta la victoria siempre? What is the meaning of obi? How to use cricut explore air 2? How to transfer ownership on discord? What is the meaning of inducement? What is a guardian angel meaning? What are the best states to retire in financially 2020? Tricks to get a toddler to drink when he has the flu? What is the meaning of gradation? What does deficiency mean? How to allocate more ram to minecraft? Should i check in with busy who seems super busy? linked in request tips? How to tweet? What does sphere mean for glasses? How to get sensation back? How long does it take to get pregnant after sex? What breed of dog does the u.s. secret service exclusively use? What time is it in beijing china? Which pipette tips to use? What does defer mean? What is the meaning of lis? Tips on how to get things up when you live on 3rd floor? What is seroquel? Where to get frosted tips? What is tajin? What does bae mean in text? where can i by hamburger helper tune casserole What is the meaning 333? What does articulation mean? What does term mean? What does wte mean? What does no atomizer mean? How to find contribution margin? How to get rid of the timeline tips in windows 10? How to do the eddy's magic tricks? How to pronounce pecan? How to put lights on a christmas tree? What does 1111 mea? How to train your dog cool tricks? What is the meaning of sucks? What does this sign mean? What does deceive mean? What does it mean when someone calls you b? How to facetime android? How to install a garbage disposal? What channel is cbs? Driving video game where you pull off tricks in parking garage? What is the meaning of customer service? How to make mac dark mode? What does dialect mean? What makes your finger tips turn white? How to play cricket? What does nf stand for? What time does the super bowl start in california? how to add helper address on cisco router How to write a conclusion for a research paper? What does waxing poetic mean? What do tire sizes mean? How to buy bitcoin? How to buy tips ameritrade? When will ethereum stop mining linus tech tips? How to invest in the stock market? Lotro how to disable tutorial tips? Reddit, where to learn magic tricks? Tips on how to please a man? How to add a signature in word? Who made magic tricks a big deal? What time does tropical smoothie open? How to get pregnant fast? ups driver helper what to bring on first day how to download video download helper doesn't recognize videos in firefox windows 10 How to sous vide steak? What is the meaning of an open relationship? How long to bake meatloaf? How to copy a formula in excel? What is the meaning of oem? What does a black flag mean? What is being right brained meaning? What does pang mean? What are benchmarks? What does mano mean in spanish? What epoch are we in? Tips for learning how to draw cartoon faces off of real person? What is the spiritual meaning of a toad? What is the meaning of earmarked? 101 how to do magic tricks at home? What is collision insurance? marriage helper how to deal with an angry spouse What is fate and destiny meaning? What is quiche? How to see posts you've liked on instagram? What does tia mean? Tips on teaching yourself how to sing forum? How to start a lawn mower? What time does arbys close? What does 👀 mean sexually? How to fight? How to become an author? What are burn pits? Tips on how to fight better? What does thrive mean? What does curbside pick up mean? How to make an airplane that does tricks? How to make cinnamon rolls? How to remove gel tips? What is entrepreneurship?