Higgs to photon decay + neutrino

In summary: I'm not sure how you would go about doing that.You can see from these diagrams that there is a bunch of junk you can get along with your Higgs; jets (from the quarks), extra leptons, missing energy. There is also lots of junk that can come from higher-order diagrams than those four. It gets tricky.I know it's kind of rough reading for high-school level, but do you know that the ATLAS public results are all here?: https://twiki.cern.ch/twiki/bin/view/AtlasPublic/HiggsPublicResultsA recent diphoton analysis is here: http://cds.cern.ch/record/1523698/files/AT
  • #1
da_noon
2
0
Hello,

I'm currently in my last year of high school and I'm doing a project about the higgs particle decaying to two photons. I am using HYPATIA to analyse ATLAS events. When a higgs boson decays into two photons, you can see activity in the electromagnetic calorimeter without seeing a track pointing to it in the tracker (because photons don't have charge). To mark an event as a Higgs particle decaying into two photons requires some criteria.
Can you mark an event as a higgs particle decaying into two photons if there are also neutrino's? Is it possible that a higgs particle decays into two photons and that the neutrino's are just some kind of noise?

I'm very sorry if I'm being vague, but I'm not really good in explaining my question.

Thanks in advance!
 
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  • #2
I don't know this stuff so can't answer your question but one thing you should be aware of, just in case you are not, is that neutrinos are practically impossible to detect so the odds of being able to detect their presence for any given collision are zero for all practical purposes.
 
  • #3
Thank you, I am aware of that, but HYPATIA knows if there is momentum and energy missing because of the conservation of energy and momentum. The missing energy and momentum is displayed as a neutrino, because it probably is one. All other particles can be detected by the detector. The neutrino is not really detected, but the missing energy and momentum is.
 
  • #4
How much missing energy is in the event? Is this more likely due to a neutrino or to mismeasurement?
 
  • #6
da_noon said:
Hello,

I'm currently in my last year of high school and I'm doing a project about the higgs particle decaying to two photons. I am using HYPATIA to analyse ATLAS events. When a higgs boson decays into two photons, you can see activity in the electromagnetic calorimeter without seeing a track pointing to it in the tracker (because photons don't have charge). To mark an event as a Higgs particle decaying into two photons requires some criteria.
Can you mark an event as a higgs particle decaying into two photons if there are also neutrino's? Is it possible that a higgs particle decays into two photons and that the neutrino's are just some kind of noise?

I'm very sorry if I'm being vague, but I'm not really good in explaining my question.

Thanks in advance!

Yeah it can happen like that. Here are the most common ways Higgses can be produced:

Higgs_prod_graphs_new2.jpg


The purple diagram shows the Higgs being produced along with vector bosons. If the vector boson is a Z, then the Z decays like 20% of the time (or some such) into a neutrino-antineutrino pair, which escapes the detector and gives you your missing energy. I don't know details like how much, I'm not an experimentalist :p.

You can see from these diagrams that there is a bunch of junk you can get along with your Higgs; jets (from the quarks), extra leptons, missing energy. There is also lots of junk that can come from higher-order diagrams than those four. It gets tricky.

I know it's kind of rough reading for high-school level, but do you know that the ATLAS public results are all here?: https://twiki.cern.ch/twiki/bin/view/AtlasPublic/HiggsPublicResults

A recent diphoton analysis is here: http://cds.cern.ch/record/1523698/files/ATLAS-CONF-2013-012.pdf

In the analysis they describe all the different kinds of events they count, though it is not light reading and there is quite a bit of jargon.

In figure 1 you can see a bit of an overview of the event selection process, and you see here they do consider events with Z's going to neutrinos in there. All the details of the cuts they make are in there, but there are a lot of them on all sorts of different properties of the events, it's not very nice to dig through.

For whatever simplified thing you are doing, though, you can probably ignore a lot of that. Most higgses are produced by gluon-gluon fusion (like 95% or something) and if you just count events with two photons (with high enough transverse momenta) and no other junk then there might be a visible signal in there these days. In fact I'm pretty certain there is.
 
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  • #7
kurros said:
If the vector boson is a Z, then the Z decays like 20% of the time (or some such) into a neutrino-antineutrino pair, which escapes the detector and gives you your missing energy. I don't know details like how much, I'm not an experimentalist :p.
Calculating those cross-sections is theory :p.

I know it's kind of rough reading for high-school level, but do you know that the ATLAS public results are all here?
I guess if he is analyzing ATLAS data, he as access to non-public documents as well.

For whatever simplified thing you are doing, though, you can probably ignore a lot of that. Most higgses are produced by gluon-gluon fusion (like 95% or something) and if you just count events with two photons (with high enough transverse momenta) and no other junk then there might be a visible signal in there these days. In fact I'm pretty certain there is.
I did not see a plot with such a simple selection, but I would expect without additional cuts (like isolation - "not too much junk close to the photons", or the direction of the photons) you don't see a real peak, you would get way too much background.
 
  • #8
mfb said:
I did not see a plot with such a simple selection, but I would expect without additional cuts (like isolation - "not too much junk close to the photons", or the direction of the photons) you don't see a real peak, you would get way too much background.

Yeah that's probably necessary. For that analysis it looks like the main cuts are:

"The transverse energies for the leading and sub-leading photons are required to be larger than 40 GeV and 30 GeV, respectively, and both need to be within the fiducial calorimeter region of |η| < 2.37"

"…the scalar sum of the transverse momenta of all tracks with pT > 1 GeV in a cone of size ∆R = 0.2 around each photon is required to be less than 2.6 GeV."

"…the transverse energy sum of positive-energy topological clusters deposited
in the calorimeter around each photon in a cone of ∆R = 0.4 is required to be less than 6 GeV."

There is then some tricky stuff about only applying these cuts to tracks originating from the same vertex as the photons, with some neural net magic to match the photons to particular vertices. Hopefully the OP already has the events separated out into stuff believed to originate from a single vertex though... anyway I guess they already have some of that sorted out if they are thinking about this analysis at all.
 
  • #9
Can we possibly take this over the poster's head any faster? High school, people! High school!

HYPATIA is a stripped down analysis framework intended for high school students to learn about ATLAS events. You can find out about it here: http://hypatia.phys.uoa.gr/ Many QuarkNet teams use it.

The first thing to check - before deciding that there are additional interesting particles in the event (just like the real scientists do) is to determine if this missing energy is real. It is entirely possible that it's just measurement noise. That's why I asked how much there was. If it's 1 MeV, won't you feel a little silly?
 

1. What is Higgs to photon decay + neutrino?

Higgs to photon decay + neutrino is a process in which the Higgs boson, a subatomic particle that gives other particles mass, decays into a photon and a neutrino. This process is predicted by the Standard Model of particle physics.

2. How does Higgs to photon decay + neutrino occur?

Higgs to photon decay + neutrino occurs through the weak nuclear force, which is responsible for radioactive decay and nuclear fusion. In this process, the Higgs boson interacts with other particles, emitting a photon and a neutrino as it decays into a lower energy state.

3. What is the significance of Higgs to photon decay + neutrino?

Higgs to photon decay + neutrino is important because it provides evidence for the existence of the Higgs boson and helps scientists understand the mechanism of mass generation in the universe. This process also helps to test the predictions of the Standard Model and could potentially lead to the discovery of new physics beyond the Standard Model.

4. How is Higgs to photon decay + neutrino detected?

Higgs to photon decay + neutrino can be detected in large particle accelerators, such as the Large Hadron Collider (LHC) at CERN. By analyzing the collision data from these experiments, scientists can look for the specific signatures of a photon and a neutrino being produced from the decay of a Higgs boson.

5. What are the potential applications of studying Higgs to photon decay + neutrino?

Studying Higgs to photon decay + neutrino can help us better understand the fundamental building blocks of the universe and potentially lead to new technologies. It could also provide insights into the nature of dark matter, which is still a mystery to scientists. Additionally, the study of Higgs to photon decay + neutrino may help us develop new methods for detecting and harnessing the power of neutrinos, which are elusive particles with unique properties.

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