LHC experiments join forces to zoom in on the Higgs boson

March 17, 2015 by Cian O'luanaigh, CERN
Candidate Higgs boson event from collisions between protons in the CMS detector on the LHC. From the collision at the centre, the particle decays into two photons (dashed yellow lines and green towers) Credit: CMS/CERN

Today during the 50th session of "Rencontres de Moriond" in La Thuile Italy, ATLAS and CMS presented for the first time a combination of their results on the mass of the Higgs boson. The combined mass of the Higgs boson is mH = 125.09 ± 0.24 (0.21 stat. ± 0.11 syst.) GeV, which corresponds to a measurement precision of better than 0.2%. The Higgs boson is an essential ingredient of the Standard Model of particle physics, the theory that describes all known elementary particles and their interactions. The Brout-Englert-Higgs mechanism, through which the existence of the Higgs boson was predicted, is believed to give mass to all elementary particles. It is the most precise measurement of the Higgs boson mass yet and among the most precise measurements performed at the LHC to date.

"Collaboration is really part of our organization's DNA", said CERN Director General Rolf Heuer. "I'm delighted to see so many brilliant physicists from ATLAS and CMS joining forces for the very first time to obtain this important measurement at the LHC."

The Higgs boson decays into various different particles. For this measurement, results on the two decay channels that best reveal the mass of the Higgs boson have been combined (Higgs boson decaying to two photons and to 4 leptons, leptons being electron or muon here). Each experiment has found a few hundred events in the Higgs to photons channel and a few tens in the Higgs to leptons channel, using the data collected at the LHC in 2011 and 2012 at centre-of-mass energies of 7 and 8 TeV, having examined about 4000 trillion proton-proton collisions. The two collaborations worked together and reviewed the analyses and their combination. Experts of the analyses and of the different parts of the detectors that play a major role in this measurement were closely involved.

"The Higgs Boson was discovered at the LHC in 2012 and the study of its properties has just begun. By sharing efforts between ATLAS and CMS, we are going to understand this fascinating particle in more detail and study its behaviour", said CMS spokesperson Tiziano Camporesi.

Candidate Higgs boson event from collisions between protons in the ATLAS detector on the LHC. From the collision at the centre, the particle decays into four muons (red tracks) Credit: ATLAS/CERN
"CMS and ATLAS use different detector technologies and different detailed analyses to determine the Higgs mass. The measurements made by the experiments are quite consistent, and we have learnt a lot by working together, which stands us in good stead for further combinations.", said ATLAS spokesperson Dave Charlton.

The Standard Model does not predict the mass of the Higgs boson itself and therefore it must be measured experimentally. However, once supplied with a Higgs mass, the Standard Model does make predictions for all the other properties of the Higgs boson, which can then be tested by the experiments. This mass combination represents the first step towards a combination of other measurements of Higgs boson properties, which will involve also the other decays.

"While we are just getting ready to restart the LHC, it is admirable to notice the precision already achieved by the two experiments and the compatibility of their results. This is very promising for LHC Run 2", said CERN Director of Research Sergio Bertolucci.

This result was achieved by bringing together physicists of the ATLAS and CMS collaborations, representing together more than 5,000 scientists from over 50 different countries.

Up to now, increasingly precise measurements from the two experiments have established that all observed properties of the Higgs boson, including its spin, parity and interactions with other particles are consistent with the Standard Model Higgs boson. With the upcoming combination of other Run 1 Higgs results from the two experiments and with higher energy and more collisions to come during LHC Run 2, physicists expect to increase even more the precision of the Higgs mass and explore in more detail the particle's properties. During Run 2, they will be able to combine their results promptly and thus increase the LHC's sensitivity to effects that could hint at new physics beyond the Standard Model.

Explore further: Broadest set of results to date about the properties of the Higgs boson

More information: Paper will be made available on ArXiv within a few days.

Related Stories

ATLAS sees Higgs boson decay to fermions

November 28, 2013

The ATLAS experiment at CERN has released preliminary results that show evidence that the Higgs boson decays to two tau particles. Taus belong to a group of subatomic particles called the fermions, which make up matter. ...

The Higgs boson: One year on

July 5, 2013

A year ago today, physicists from the ATLAS and CMS experiments at CERN proudly announced the discovery of a new boson looking very much like the Higgs boson.

Evidence found for the Higgs boson direct decay into fermions

June 22, 2014

For the first time, researchers at CERN have found evidence for the direct decay of the Higgs boson into fermions—another strong indication that the particle discovered in 2012 behaves in the way the standard model of particle ...

Recommended for you

New thermoelectric material delivers record performance

January 17, 2019

Taking advantage of recent advances in using theoretical calculations to predict the properties of new materials, researchers reported Thursday the discovery of a new class of half-Heusler thermoelectric compounds, including ...

Zirconium isotope a master at neutron capture

January 17, 2019

The probability that a nucleus will absorb a neutron is important to many areas of nuclear science, including the production of elements in the cosmos, reactor performance, nuclear medicine and defense applications.

14 comments

Adjust slider to filter visible comments by rank

Display comments: newest first

El_Nose
5 / 5 (7) Mar 17, 2015
authors of scientific articles are going to have to start using quadrillion and quintillion when talking about LHC collision rates. As a reader of a scientific article it is not unusual for these numbers to already be in our vocabularies.
vic1248
2.5 / 5 (4) Mar 17, 2015
With all objectivity in mind, all what that means is that it is a "re-run" of the experiment that took place and resulted in the announcement of the discovery of the Higgs Boson Particle in July of 2012.

Now, it is imperative to discern that there can only be one Higgs Boson Particle that fits the Particle Physics Standard Model for it to be correct, that is spin-0, scalar Higgs Boson Particle, aka the God's Particle; otherwise, the Particle Physics Standard Model is rendered "incomplete," mind you what's missing is the "core."
Noumenon
4.2 / 5 (5) Mar 17, 2015
Now, it is imperative to discern that there can only be one Higgs Boson Particle that fits the Particle Physics Standard Model for it to be correct, that is spin-0, scalar Higgs Boson Particle, aka the God's Particle; otherwise, the Particle Physics Standard Model is rendered "incomplete," mind you what's missing is the "core."


The SM can be extended to accommodate multiple Higgs fields, so it wouldn't be intrinsically incomplete if more were discovered.
rufusgwarren
2.8 / 5 (6) Mar 17, 2015
The "Higgs" is simply a field event and not a particle. Proof, should show the nature of the radiant static field of the Higgs. From what I've read, that does not seem possible; hence, necessary and sufficient is not established. Defining short lived events as particle decay is somewhat bizarre, since there does not exist an existence proof of what happens if we did split the proton. It is only someone's interpretation to fit a misguided model developed in the 20th century when much less was known. Really, it is time we moved on. Unless the work is to see if we really can split the proton.
Nanowill
1 / 5 (3) Mar 17, 2015
Q. As the electron at 0.511 MeV exhibits mass, if the Higgs "gives particles mass" how many 125GeV Higgs particles are there in an electron?

rufusgwarren: The proton cannot be split as it is a single quantum energy, the partial quark charges are simply near field artifacts of a field distributed in three dimensions, which is why they cannot be separated. The proton charge relates to alpha.hbar.c, so for a uniform field distribution an interaction in one dimension would look like alpha.hbar/c^1/3 and a two dimensional interaction would be alpha.hbar.c^2/3, i.e. partial charges of 1/3 and 2/3.

The Higgs data is probably just an excited state at 1/alpha the proton energy. Note alpha is a predominant dimensionless factor in the fermions and the proton, and no doubt also in the Higgs.

Using Higgs as a mass parameter, what is the Higgs mass of the average Fairy? Speculation based on nonsense leads to more nonsense, and larger budgets.
tommo
3 / 5 (4) Mar 17, 2015
With many considering the HIggs a mathematical construct to elucidate the results with a compliant matrix.

To me the fundamental question is more, "What is an electron?". Sorry, you can't define it with that much charge & mass and activity below relativistic velocity, noting the recent news of creating electrons-positrons using photons & my own observations that many electron transactions involve photons.
jsdarkdestruction
3 / 5 (2) Mar 18, 2015
the Particle Physics Standard Model is rendered "incomplete," mind you what's missing is the "core."

1. Multiple higgs is not a problem that can't be incorporated into the standard model.
2. Which brings me to my next point, let's say with the higher energies CERN makes a finding showing they were wrong about finding the higgs. Say they prove w/o a doubt higgs doesn't exist even. That means the current theory of what gives particles mass needs to be reworked. The standard model as a whole still stands with what we do know.
3. It is wrong to say the finding of the higgs completed the standard model. Much needs to be worked out still. The graviton and dark matter are particles still not found yet.
Dethe
1 / 5 (4) Mar 18, 2015
The Standard Model actually doesn't require any Higgs boson, only Higgs field. The mass of Higgs boson doesn't follow from any standard formulation of SM, from any equation and it must be determined experimentally. So that the Higgs boson actually does violate the Standard Model, being the lightest member of supersymmetric extension of SM.
Torbjorn_Larsson_OM
4 / 5 (4) Mar 18, 2015
@jsdd: You can't 'undiscover' the already found field. So SM must be considered sound, even as the details are worked out to more precision and more consequences.

"graviton and dark matter are particles still not found yet."

Those, as well as aspects of neutrino physics I think, are not included in the SM field description. You can think of it as "new phenomena", non-SM physics, if you will. They are no threat to the model in that way.

What can happen is the way that GR embedded newtonian gravity, that string physics embed quantum field theory.* It should happen latest at Planck scales, where field particles are mere effective descriptions that lose validity.

*Of course there could be an earlier combination with gravity, but i doubt it. It too loses validity at Planck scales...
richard_f_cronin
1 / 5 (1) Mar 18, 2015
rufusgwarren - Thank you, sir !!

Your words: "The "Higgs" is simply a field event and not a particle." I've long held the same thought.

Just as a planetary mass in motion curves space and generates a gravitational field. A charged particle (i.e. an electron) in motion generates a magnetic field. The weak force is a field property of vibration that surges thru the nucleus of a radioactive isotope before it emits a decay particle. The Higgs field is generated by nucleons in motion. The "quantum bounce" at the core of a White Hole is due to Zero Point Energy, acting like a spring to regurgitate the matter drawn into an "apparent" Black Hole as well as introduce new energy (and mass) into our Universe. (Carlo Rovelli and Francesca Vidotto).

Both the First and Second Laws of classical Thermodynamics break down at the core of a White Hole. New matter is created to fill the infinite and ever-expanding Universe.
jsdarkdestruction
not rated yet Mar 18, 2015
Torborn, you have completely misunderstood what I was saying.
. I was explaining to him that even if higgs doesn't exis(which it quite unlikely. I say it for the sake of argument) t it doesn't mean the whole standard model is wrong.
PhysicsMatter
3.7 / 5 (3) Mar 21, 2015
They are trying to cover up the fact that 2012 experiment was inconclusive as concluded by Danish researchers in their 2014 Physical Review Letters paper. LHC group could not conclusively discover Higgs particle before LHC "blew up" and as results they had to rebuild it during last two years.

I wish them success but the context of this endeavor looks more and more suspicious when many personal interests seem to overshadow science.

What I do not like is fact that no one outside the LHC group with their vested interests will be able to verify their results experimentally what scientific method requires.

Otherwise we are dealing with alchemy.
viko_mx
1 / 5 (3) Mar 22, 2015
Indeed there is fasion trend in science which make alchemics very popular and noisy in mass media. They do not guide itself by scientific ethics and do not use scientific methods, but only by their pasion to abstract theories and the common between them is that must be maximum faraway from the idea for the Creator. These people constantly trying to fit the reality to their theories and present their invented reality with comic pride and diligence to the public.
El_Nose
not rated yet May 04, 2015
@rufusgwarren

logically all the particles are a field and not a particle. there is only one electron and its field becomes viable in certian conditions near collections of neutron and proton fields.

Please sign in to add a comment. Registration is free, and takes less than a minute. Read more

Click here to reset your password.
Sign in to get notified via email when new comments are made.