Featured Research

from universities, journals, and other organizations

ATLAS and CMS experiments present Higgs search status

Date:
December 13, 2011
Source:
CERN
Summary:
In a seminar held at CERN Dec. 13, the ATLAS and CMS experiments presented the status of their searches for the Standard Model Higgs boson. Their results are based on the analysis of considerably more data than those presented at the summer conferences, sufficient to make significant progress in the search for the Higgs boson, but not enough to make any conclusive statement on the existence or non-existence of the elusive Higgs. The main conclusion is that the Standard Model Higgs boson, if it exists, is most likely to have a mass constrained to the range 116-130 GeV by the ATLAS experiment, and 115-127 GeV by CMS. Tantalizing hints have been seen by both experiments in this mass region, but these are not yet strong enough to claim a discovery.

An event showing four muons (red tracks) from a proton-proton collision in ATLAS. This event is consistent with two Z particles decaying into two muons each. Such events are produced by Standard Model processes without Higgs particles. They are also a possible signature for Higgs particle production, but many events must be analysed together in order to tell if there is a Higgs signal.
Credit: ATLAS Collaboration / 2011 CERN

In a seminar held at CERN[1] Dec. 13, the ATLAS[2] and CMS[3] experiments presented the status of their searches for the Standard Model Higgs boson. Their results are based on the analysis of considerably more data than those presented at the summer conferences, sufficient to make significant progress in the search for the Higgs boson, but not enough to make any conclusive statement on the existence or non-existence of the elusive Higgs.

Related Articles


The main conclusion is that the Standard Model Higgs boson, if it exists, is most likely to have a mass constrained to the range 116-130 GeV by the ATLAS experiment, and 115-127 GeV by CMS. Tantalising hints have been seen by both experiments in this mass region, but these are not yet strong enough to claim a discovery.

Higgs bosons, if they exist, are very short lived and can decay in many different ways. Discovery relies on observing the particles they decay into rather than the Higgs itself. Both ATLAS and CMS have analysed several decay channels, and the experiments see small excesses in the low mass region that has not yet been excluded.

Taken individually, none of these excesses is any more statistically significant than rolling a die and coming up with two sixes in a row. What is interesting is that there are multiple independent measurements pointing to the region of 124 to 126 GeV. It's far too early to say whether ATLAS and CMS have discovered the Higgs boson, but these updated results are generating a lot of interest in the particle physics community.

"We have restricted the most likely mass region for the Higgs boson to 116-130 GeV, and over the last few weeks we have started to see an intriguing excess of events in the mass range around 125 GeV," explained ATLAS experiment spokesperson Fabiola Gianotti. "This excess may be due to a fluctuation, but it could also be something more interesting. We cannot conclude anything at this stage. We need more study and more data. Given the outstanding performance of the LHC this year, we will not need to wait long for enough data and can look forward to resolving this puzzle in 2012."

"We cannot exclude the presence of the Standard Model Higgs between 115 and 127 GeV because of a modest excess of events in this mass region that appears, quite consistently, in five independent channels," explained CMS experiment Spokesperson, Guido Tonelli. "The excess is most compatible with a Standard Model Higgs in the vicinity of 124 GeV and below but the statistical significance is not large enough to say anything conclusive. As of today what we see is consistent either with a background fluctuation or with the presence of the boson. Refined analyses and additional data delivered in 2012 by this magnificent machine will definitely give an answer."

Over the coming months, both experiments will be further refining their analyses in time for the winter particle physics conferences in March. However, a definitive statement on the existence or non-existence of the Higgs will require more data, and is not likely until later in 2012.

The Standard Model is the theory that physicists use to describe the behaviour of fundamental particles and the forces that act between them. It describes the ordinary matter from which we, and everything visible in the Universe, are made extremely well. Nevertheless, the Standard Model does not describe the 96% of the Universe that is invisible. One of the main goals of the LHC research programme is to go beyond the Standard Model, and the Higgs boson could be the key.

A Standard Model Higgs boson would confirm a theory first put forward in the 1960s, but there are other possible forms the Higgs boson could take, linked to theories that go beyond the Standard Model. A Standard Model Higgs could still point the way to new physics, through subtleties in its behaviour that would only emerge after studying a large number of Higgs particle decays. A non-Standard Model Higgs, currently beyond the reach of the LHC experiments with data so far recorded, would immediately open the door to new physics, whereas the absence of a Standard Model Higgs would point strongly to new physics at the LHC's full design energy, set to be achieved after 2014. Whether ATLAS and CMS show over the coming months that the Standard Model Higgs boson exists or not, the LHC programme is opening the way to new physics.

Notes:

[1] CERN, the European Organization for Nuclear Research, is the world's leading laboratory for particle physics. It has its headquarters in Geneva. At present, its Member States are Austria, Belgium, Bulgaria, the Czech Republic, Denmark, Finland, France, Germany, Greece, Hungary, Italy, the Netherlands, Norway, Poland, Portugal, Slovakia, Spain, Sweden, Switzerland and the United Kingdom. Romania is a candidate for accession. Israel is an Associate Member in the pre-stage to Membership. India, Japan, the Russian Federation, the United States of America, Turkey, the European Commission and UNESCO have Observer status.

[2] ATLAS is a particle physics experiment at the Large Hadron Collider at CERN. The ATLAS Collaboration is a virtual United Nations of 38 countries. The 3000 physicists come from more than 174 universities and laboratories and include 1000 students.

[3] The Compact Muon Solenoid (CMS) experiment is one of the largest international scientific collaborations in history, involving more than 3000 scientists, engineers, and students from 172 institutes in 40 countries.


Story Source:

The above story is based on materials provided by CERN. Note: Materials may be edited for content and length.


Cite This Page:

CERN. "ATLAS and CMS experiments present Higgs search status." ScienceDaily. ScienceDaily, 13 December 2011. <www.sciencedaily.com/releases/2011/12/111213105806.htm>.
CERN. (2011, December 13). ATLAS and CMS experiments present Higgs search status. ScienceDaily. Retrieved March 26, 2015 from www.sciencedaily.com/releases/2011/12/111213105806.htm
CERN. "ATLAS and CMS experiments present Higgs search status." ScienceDaily. www.sciencedaily.com/releases/2011/12/111213105806.htm (accessed March 26, 2015).

Share This


More From ScienceDaily



More Matter & Energy News

Thursday, March 26, 2015

Featured Research

from universities, journals, and other organizations


Featured Videos

from AP, Reuters, AFP, and other news services

Amazon Complains U.S. Is Too Slow To Regulate Drones

Amazon Complains U.S. Is Too Slow To Regulate Drones

Newsy (Mar. 25, 2015) Days after getting approval to test certain commercial drones, Amazon says the Federal Aviation Administration is dragging its feet on the matter. Video provided by Newsy
Powered by NewsLook.com
Smartphone Use Changing Our Brain and Thumb Interaction, Say Researchers

Smartphone Use Changing Our Brain and Thumb Interaction, Say Researchers

Reuters - Innovations Video Online (Mar. 25, 2015) European researchers say our smartphone use offers scientists an ideal testing ground for human brain plasticity. Dr Ako Ghosh&apos;s team discovered that the brains and thumbs of smartphone users interact differently from those who use old-fashioned handsets. Jim Drury went to meet him. Video provided by Reuters
Powered by NewsLook.com
China Wants to Export Its Steel Problem

China Wants to Export Its Steel Problem

Reuters - Business Video Online (Mar. 25, 2015) China is facing a crisis with a glut of steel and growing public anger over the pollution created by production. In a move to solve the problem, some steel mills are looking to relocate overseas. Jane Lanhee Lee reports. Video provided by Reuters
Powered by NewsLook.com
Robot Stays on Its Feet Despite Punishment

Robot Stays on Its Feet Despite Punishment

Reuters - Innovations Video Online (Mar. 24, 2015) Robotic engineers have modelled a two-legged robot to be fast and agile like an ostrich. The design is more efficient and stable than bipedal robots built to move like humans, according to its creators who abuse the poor machine to test its skills. Ben Gruber has more. Video provided by Reuters
Powered by NewsLook.com

Search ScienceDaily

Number of stories in archives: 140,361

Find with keyword(s):
Enter a keyword or phrase to search ScienceDaily for related topics and research stories.

Save/Print:
Share:

Breaking News:

More Coverage


Promising Signs for the Existence of the Higgs Boson

Dec. 13, 2011 Today's announcement from the Large Hadron Collider (LHC) at CERN points to promising signs for the existence of the Higgs boson. Weizmann Institute scientists have been prominent participants ... read more

Possible Hints of Higgs Boson Remain in Latest Analyses, Physicists Say

Dec. 13, 2011 Two experiments at the Large Hadron Collider have nearly eliminated the space in which the Higgs boson could dwell, scientists announced in a seminar held at CERN Dec. 13. However, the ATLAS and CMS ... read more

Physicists Smell but Don't Yet Taste Higgs

Dec. 13, 2011 In a seminar held at CERN Dec. 13 and then repeated across Canada at multiple partnering institutions, the ATLAS and CMS experiments presented the status of their searches for the Standard Model ... read more

Physicists Help Narrow Search for Elusive Higgs Boson, a Building Block of the Universe

Dec. 13, 2011 Physicists have narrowed the search for the Higgs boson, a subatomic particle that is a building block of the universe. In an announcement made Dec. 13 in Geneva, scientists said they have found ... read more

Physicists Say They Are Near Epic Higgs Boson Discovery

Dec. 13, 2011 The Holy Grail of high-energy physics -- the predicted but elusive Higgs boson -- is almost within reach, and particle physicists around the world collaborating on making the finding are almost giddy ... read more

More Clues in the Hunt for the Higgs: Physicists Unveil the Largest Amount of Data Ever Presented for the Higgs Search

Dec. 15, 2011 Physicists have announced that the Large Hadron Collider has produced yet more tantalizing hints for the existence of the Higgs boson. The European Center for Nuclear Research in Geneva, the ... read more

Strange & Offbeat Stories


Space & Time

Matter & Energy

Computers & Math

In Other News

... from NewsDaily.com

Science News

Health News

Environment News

Technology News



Save/Print:
Share:

Free Subscriptions


Get the latest science news with ScienceDaily's free email newsletters, updated daily and weekly. Or view hourly updated newsfeeds in your RSS reader:

Get Social & Mobile


Keep up to date with the latest news from ScienceDaily via social networks and mobile apps:

Have Feedback?


Tell us what you think of ScienceDaily -- we welcome both positive and negative comments. Have any problems using the site? Questions?
Mobile: iPhone Android Web
Follow: Facebook Twitter Google+
Subscribe: RSS Feeds Email Newsletters
Latest Headlines Health & Medicine Mind & Brain Space & Time Matter & Energy Computers & Math Plants & Animals Earth & Climate Fossils & Ruins