ATLAS and CMS experiments submit Higgs search papers Geneva 7 February 2012. The Standard Model Higgs search analyses presented at CERN by the ATLAS and CMS collaborations at a seminar in December last year were today submitted for publication in the journal Physics Letters B.
After further analysis, the statistical significance of the measurements remains close to that presented at the seminar, underlining the conclusion that the Standard Model Higgs boson, if it exists, is most likely to have a mass constrained to the range 116-131 GeV by the ATLAS experiment, and 115-127 GeV by CMS. Tantalising hints have been seen by both experiments in the region 124-126 GeV; however, these are not strong enough to claim a discovery.
The results on Standard Model (SM) Higgs searches that ATLAS reported at a CERN seminar on December 13, 2011 have now been submitted for publication in three papers.
The Higgs boson is predicted to decay in several different ways, known as decay channels. Two of the papers report on searches, performed with the full data sample from 2011, in the Higgs decay channels that result in either two photons or four leptons in the final state.
These are two of the channels that are presently most sensitive in the low mass range where a SM Higgs is generally expected to appear. The third paper reports on the combination of the results from these two channels with those from other channels to provide a more sensitive search, extending over a larger mass range. This last paper was submitted simultaneously with a similar paper from the CMS experiment.
The results of the analyses documented in the papers are essentially unchanged from those presented at the seminar, and the overall conclusion also remains the same. If the SM Higgs exists, it is most likely to have a mass in the range 116-131 GeV; moreover, despite tantalizing hints in the region of 126 GeV, more data are needed to resolve whether or not the SM Higgs exists. The requisite data should be available by the end of the 2012 LHC proton-proton run.
Experimental limits from ATLAS on Standard Model (SM) Higgs production in the mass range 110-600 GeV. The solid curve reflects the observed experimental limits, expressed in terms of the ratio (µ) of the observed cross-section to the cross-section predicted by the SM (vertical axis), for the production of Higgs for each possible mass value (horizontal axis).
The region for which the solid curve dips below the horizontal line at the value of 1 is excluded with a 95% confidence level (CL). The dashed curve shows the expected limit in the absence of the Higgs boson, based on simulations. The green and yellow bands correspond (respectively) to 68%, and 95% confidence level regions from the expected limits.
For an explanation of this plot, please click here.
CMS Higgs boson search results from 2010-2011 data samples
This week the CMS collaboration will publish the results of its search for the Higgs boson that were presented at CERN in December 2011 [1].
Nine papers will be submitted for publication using the entire data sample of proton-proton collisions collected up to the end of 2011. These data amount to 4.7 fb-1 of integrated luminosity [2]. Eight out of the nine papers discuss the individual analyses of a number of predicted Higgs decay channels. These papers include some improvements in the analyses, most notably in the photon pair decay channel [3].
The ninth paper, submitted today simultaneously with a similar paper by the ATLAS collaboration, presents the combined result of the individual channels [4].
The significance of the largest excess (at 124 GeV) has increased slightly to 2.1 standard deviations [5]. There is no substantive change in our conclusions: the question of the existence of the Standard Model Higgs boson can only be resolved with the collection of more data during 2012.
The ATLAS Collaboration submitted the ATLAS Higgs boson search results simultaneously.
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