FASER (ForwArd Search ExpeRiment) is planned to be one of the eight particle physics experiments in 2022 at the
Large Hadron Collider
The Large Hadron Collider (LHC) is the world's largest and highest-energy particle collider. It was built by the European Organization for Nuclear Research (CERN) between 1998 and 2008 in collaboration with over 10,000 scientists and hundre ...
at
CERN
The European Organization for Nuclear Research, known as CERN (; ; ), is an intergovernmental organization that operates the largest particle physics laboratory in the world. Established in 1954, it is based in a northwestern suburb of Gene ...
. It is designed to both search for new light and weakly coupled
elementary particle
In particle physics, an elementary particle or fundamental particle is a subatomic particle that is not composed of other particles. Particles currently thought to be elementary include electrons, the fundamental fermions (quarks, leptons, antiq ...
s, and to study the interactions of high-energy
neutrino
A neutrino ( ; denoted by the Greek letter ) is a fermion (an elementary particle with spin of ) that interacts only via the weak interaction and gravity. The neutrino is so named because it is electrically neutral and because its rest mass is ...
s.
The experiment is installed in the service tunnel TI12, which is 480 m downstream from the interaction point used by the
ATLAS
An atlas is a collection of maps; it is typically a bundle of maps of Earth or of a region of Earth.
Atlases have traditionally been bound into book form, but today many atlases are in multimedia formats. In addition to presenting geographi ...
experiment.
This tunnel was formerly used to inject the beam from the
SPS
SPS may refer to:
Law and government
* Agreement on the Application of Sanitary and Phytosanitary Measures of the WTO
* NATO Science for Peace and Security
* Single Payment Scheme, an EU agricultural subsidy
* The Standard Procurement System, ...
into the
LEP accelerator. In this location, the FASER experiment is placed into an intense and highly collimated beam of both neutrinos as well as possible new particles. Additionally, it is shielded from ATLAS by about 100 meters of rock and concrete, providing a low background environment. The FASER experiment was approved in 2019 and will start taking data during Run 3 of the LHC, starting in 2022.
New physics searches
The primary goal of the FASER experiment is to search for new light and weakly interacting particles, that have not been discovered yet, such as
dark photon
The dark photon (also hidden, heavy, para-, or secluded photon) is a hypothetical hidden sector particle, proposed as a force carrier similar to the photon of electromagnetism but potentially connected to dark matter. In a minimal scenario, thi ...
s,
axion
An axion () is a hypothetical elementary particle postulated by the Peccei–Quinn theory in 1977 to resolve the strong CP problem in quantum chromodynamics (QCD). If axions exist and have low mass within a specific range, they are of interest ...
-like particles and
sterile neutrino
Sterile neutrinos (or inert neutrinos) are hypothetical particles (neutral leptons – neutrinos) that are believed to interact only via gravity and not via any of the other fundamental interactions of the Standard Model. The term ''sterile neutrin ...
s. If these particles are sufficiently light, they can be produced in rare decays of
hadron
In particle physics, a hadron (; grc, ἁδρός, hadrós; "stout, thick") is a composite subatomic particle made of two or more quarks held together by the strong interaction. They are analogous to molecules that are held together by the e ...
s. Such particles will therefore be dominantly produced in the forward direction along the collision axis, forming a highly collimated beam, and can inherit a large fraction of the LHC proton beam energy. Additionally, due to their small couplings to the
standard model
The Standard Model of particle physics is the theory describing three of the four known fundamental forces (electromagnetic, weak and strong interactions - excluding gravity) in the universe and classifying all known elementary particles. It w ...
particles and large boosts, these particles are long-lived and can easily travel hundreds of meters without interacting before they decay to standard model particles. These decays lead to a spectacular signal, the appearance of highly energetic particles, which FASER aims to detect.
Neutrino physics
The LHC is the highest energy particle collider built so far, and therefore also the source of the most energetic neutrinos created in a controlled laboratory environment. Collisions at the LHC lead to a large flux of high-energy neutrinos of all
flavours, which are highly collimated around the beam collision axis and stream through the FASER location. The dedicated sub-detector
FASERν (FASERnu) is designed to detect these neutrinos. It will record and study thousands of neutrino interactions, which allows to measure neutrino cross sections at
TeV
TEV may refer to:
* Transient Earth Voltage: a term for voltages appearing on the metal work of switchgear due to internal partial discharges
* TeV, or teraelectronvolt or trillion electron volt, a measure of energy
* Total Enterprise Value, a ...
energies where they are currently unconstrained.
FASERnu will be capable of exploring the following physics domains:
# Interactions of all neutrino flavors and anti-neutrinos and measurement of the cross-section at TeV energy scales.
# With the ability to detect ~10000 neutrinos during its run period, FASERnu will be able to see the highest number of nucleus-tau neutrino and nucleus-electron neutrino interactions and will open ample opportunities for neutrino studies.
# The collaboration will carry out very precise measurements of the rate of muon neutrino interactions at an energy scale never explored before.
In 2021, the FASER collaboration announced the observation of the first neutrino interaction candidates at the LHC.
Detector
Located at the front end of FASER is the FASERν neutrino detector. It consists of many layers of
emulsion
An emulsion is a mixture of two or more liquids that are normally immiscible (unmixable or unblendable) owing to liquid-liquid phase separation. Emulsions are part of a more general class of two-phase systems of matter called colloids. Although ...
films interleaved with tungsten plates as target material for neutrino interactions. Behind FASERν and at the entrance to the main detector is a charged particle veto consisting of plastic
scintillator
A scintillator is a material that exhibits scintillation, the property of luminescence, when excited by ionizing radiation. Luminescent materials, when struck by an incoming particle, absorb its energy and scintillate (i.e. re-emit the absorbe ...
s.
This is followed by a 1.5 meter long empty decay volume and a 2 meter long
spectrometer, which are placed in a 0.55
T magnetic field. The spectrometer consists of three tracking stations, composed of layers of precision
silicon strip detectors, to detect charged particles produced in the decay of long-lived particles. Located at the end is an electromagnetic
calorimeter
A calorimeter is an object used for calorimetry, or the process of measuring the heat of chemical reactions or physical changes as well as heat capacity. Differential scanning calorimeters, isothermal micro calorimeters, titration calorimete ...
.
References
External links
Official FASER websiteFASER experimentrecord on
INSPIRE-HEP INSPIRE-HEP is an open access digital library for the field of high energy physics (HEP). It is the successor of the Stanford Physics Information Retrieval System (SPIRES) database, the main literature database for high energy physics since the 1970 ...
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CERN experiments
Particle experiments
Large Hadron Collider