From CERN CMS: “CMS hunts for dark photons coming from the Higgs boson”

Cern New Bloc

Cern New Particle Event

CERN New Masthead

From CERN CMS

24 May, 2019
Ana Lopes

1
A proton–proton collision event featuring a muon–antimuon pair (red), a photon (green), and large missing transverse momentum. (Image: CERN)

They know it’s there but they don’t know what it’s made of. That pretty much sums up scientists’ knowledge of dark matter.

Fritz Zwicky discovered Dark Matter when observing the movement of the Coma Cluster., Vera Rubin a Woman in STEM denied the Nobel, did most of the work on Dark Matter.

Fritz Zwicky from http:// palomarskies.blogspot.com

Coma cluster via NASA/ESA Hubble

Astronomer Vera Rubin at the Lowell Observatory in 1965, worked on Dark Matter (The Carnegie Institution for Science)


Vera Rubin measuring spectra, worked on Dark Matter (Emilio Segre Visual Archives AIP SPL)


Vera Rubin, with Department of Terrestrial Magnetism (DTM) image tube spectrograph attached to the Kitt Peak 84-inch telescope, 1970. https://home.dtm.ciw.edu

This knowledge comes from observations of the universe, which indicate that the invisible form matter is about five to six times more abundant than visible matter.

One idea is that dark matter comprises dark particles that interact with each other through a mediator particle called the dark photon, named in analogy with the ordinary photon that acts as a mediator between electrically charged particles. A dark photon would also interact weakly with the known particles described by the Standard Model of particle physics, including the Higgs boson.

Standard Model of Particle Physics (LATHAM BOYLE AND MARDUS OF WIKIMEDIA COMMONS)

CERN CMS Higgs Event


CERN ATLAS Higgs Event

At the Large Hadron Collider Physics (LHCP) conference, happening this week in Puebla, Mexico, the CMS collaboration reported the results of its latest search for dark photons.

The collaboration used a large proton–proton collision dataset, collected during the Large Hadron Collider’s second run, to search for instances in which the Higgs boson might transform, or “decay”, into a photon and a massless dark photon. They focused on cases in which the boson is produced together with a Z boson that itself decays into electrons or their heavier cousins known as muons.

Such instances are expected to be extremely rare, and finding them requires deducing the presence of the potential dark photon, which particle detectors won’t see. For this, researchers add up the momenta of the detected particles in the transverse direction – that is, at right angles to the colliding beams of protons – and identify any missing momentum needed to reach a total value of zero. Such missing transverse momentum indicates an undetected particle.

But there’s another step to distinguish between a possible dark photon and known particles. This entails estimating the mass of the particle that decays into the detected photon and the undetected particle. If the missing transverse momentum is carried by a dark photon produced in the decay of the Higgs boson, that mass should correspond to the Higgs-boson mass.

The CMS collaboration followed this approach but found no signal of dark photons. However, the collaboration placed upper bounds on the likelihood that a signal would have been seen.

Another null result? Yes, but results such as these and the ATLAS results on supersymmetry also presented this week in Puebla, while not finding new particles or ruling out their existence, are much needed to guide future work, both experimental and theoretical.

For more details about this result, see the CMS website.

See the full article here.


five-ways-keep-your-child-safe-school-shootings
Please help promote STEM in your local schools.

Stem Education Coalition

Meet CERN in a variety of places:

Quantum Diaries
QuantumDiaries

Cern Courier

CMS
CERN CMS New