Fixed-target experiment

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Diagram of the Rutherford gold foil experiment. Gold foil experiment conclusions.svg
Diagram of the Rutherford gold foil experiment.

A fixed-target experiment in particle physics is an experiment in which a beam of accelerated particles is collided with a stationary target. The moving beam (also known as a projectile) consists of charged particles such as electrons or protons and is accelerated to relativistic speed. The fixed target can be a solid block or a liquid or a gaseous medium. [1] [2] These experiments are distinct from the collider-type experiments in which two moving particle beams are accelerated and collided. The famous Rutherford gold foil experiment, performed between 1908 and 1913, was one of the first fixed-target experiments, in which the alpha particles were targeted at a thin gold foil. [1] [3] [4]

Contents

Explanation

The energy involved in a fixed target experiment is 4 times smaller compared to that in collider with the dual beams of same energy. [5] [6] More over in collider experiments energy of two beams is available to produce new particles, while in fixed target case a lot of energy is just expended in giving velocities to the newly created particles. This clearly implies that fixed target experiments are not helpful when it comes to increasing the energy scales of experiments. [3] [7] The targeted source also wears down with number of strikes and usually require a regular replacement. Current day fixed-target experiments try to use highly resistant materials but the damage cannot be avoided entirely. [8]

The fixed target experiments have a significant advantage for experiments that require higher luminosity (rate of interaction). [5] [9] The High Luminosity Large Hadron Collider, which is an upcoming upgraded version of the Large Hadron Collider (LHC) at CERN, will attain total integrated luminosity of around in its run. [10] While luminosity scale of about have already been approached by older fixed target experiments such at the E288 led by Leon Lederman at Fermilab. [3] [11] Another advantage for fixed-target experiments is that they are easier and cheaper to build compared to the collider accelerators. [5]

Experimental facilities

NA62 experimental area at CERN that fires high-energy protons from the Super Proton Synchrotron (SPS) into a stationary beryllium target. Fte111.jpg
NA62 experimental area at CERN that fires high-energy protons from the Super Proton Synchrotron (SPS) into a stationary beryllium target.

Rutherford's gold foil experiment that led to the discovery that mass and positive charge of an atom was concentrated in a small nucleus was probably the first fixed-target experiment. Later half of the 20th century saw the rise of particle and nuclear physics facilities such as CERN's Super Proton Synchrotron (SPS) and Fermilab's Tevatron where number of fixed-target experiments led to new discoveries. 43 fixed-target experiments were conducted at the Tevatron during its run period from 1983 to 2000. [12] While proton and other beams from SPS are still used by fixed target experiments such as NA61/SHINE and COMPASS collaboration. A fixed-target facility at the LHC, called AFTER@LHC, is also being planned. [13] [14]

Physics at fixed-target experiments

COMPASS experimental area at CERN that fires muons and pions at a polarized target. Fte222.jpg
COMPASS experimental area at CERN that fires muons and pions at a polarized target.

The fixed-target experiments are mainly implemented for the intensive studies of the rare processes, dynamics at high Bjorken x, diffractive physics, spin-correlations, and numerous nuclear phenomena. [13] [14]

The experiments at Fermilab's Tevatron facility covered wide range of physics domains such as testing the theoretical predictions of quantum chromodynamics theory, studies of structure of proton, neutron and mesons, and studies of heavy quarks such as charm and bottom. Several experiments looked into CP symmetry tests. Few collaborations also studied the hyperons and the neutrinos created at fixed-target setups. [12] [15]

NA61/SHINE at the SPS is studying the phase transitions in strongly interacting matter and physics related to onset of confinement. [16] While the COMPASS experiment investigates the structure of the hadrons. [17]

AFTER@LHC aims at the studies of gluon and quark distribution inside protons and neutrons using fixed-target facilities. [13] There are possibilities to observe the W and Z bosons as well. [18] Observation and studies of the Drell-Yan pair production and quarkonium are also being looked into. [14]

Thus the number of options available to explore extreme and rare physics at the fixed-target experiments are numerous.

See also

Related Research Articles

<span class="mw-page-title-main">Tevatron</span> Defunct American particle accelerator at Fermilab in Illinois (1983–2011)

The Tevatron was a circular particle accelerator in the United States, at the Fermi National Accelerator Laboratory, east of Batavia, Illinois, and was the highest energy particle collider until the Large Hadron Collider (LHC) of the European Organization for Nuclear Research (CERN) was built near Geneva, Switzerland. The Tevatron was a synchrotron that accelerated protons and antiprotons in a 6.28 km (3.90 mi) circumference ring to energies of up to 1 TeV, hence its name. The Tevatron was completed in 1983 at a cost of $120 million and significant upgrade investments were made during its active years of 1983–2011.

<span class="mw-page-title-main">Top quark</span> Type of quark

The top quark, sometimes also referred to as the truth quark, is the most massive of all observed elementary particles. It derives its mass from its coupling to the Higgs field. This coupling yt is very close to unity; in the Standard Model of particle physics, it is the largest (strongest) coupling at the scale of the weak interactions and above. The top quark was discovered in 1995 by the CDF and DØ experiments at Fermilab.

<span class="mw-page-title-main">Large Hadron Collider</span> Particle accelerator at CERN, Switzerland

The Large Hadron Collider (LHC) is the world's largest and highest-energy particle accelerator. It was built by the European Organization for Nuclear Research (CERN) between 1998 and 2008 in collaboration with over 10,000 scientists and hundreds of universities and laboratories across more than 100 countries. It lies in a tunnel 27 kilometres (17 mi) in circumference and as deep as 175 metres (574 ft) beneath the France–Switzerland border near Geneva.

<span class="mw-page-title-main">ATLAS experiment</span> CERN LHC experiment

ATLAS is the largest general-purpose particle detector experiment at the Large Hadron Collider (LHC), a particle accelerator at CERN in Switzerland. The experiment is designed to take advantage of the unprecedented energy available at the LHC and observe phenomena that involve highly massive particles which were not observable using earlier lower-energy accelerators. ATLAS was one of the two LHC experiments involved in the discovery of the Higgs boson in July 2012. It was also designed to search for evidence of theories of particle physics beyond the Standard Model.

A collider is a type of particle accelerator that brings two opposing particle beams together such that the particles collide. Compared to other particle accelerators in which the moving particles collide with a stationary matter target, colliders can achieve higher collision energies. Colliders may either be ring accelerators or linear accelerators.

<span class="mw-page-title-main">UA2 experiment</span> Particle physics experiment at CERN

The Underground Area 2 (UA2) experiment was a high-energy physics experiment at the Proton-Antiproton Collider — a modification of the Super Proton Synchrotron (SPS) — at CERN. The experiment ran from 1981 until 1990, and its main objective was to discover the W and Z bosons. UA2, together with the UA1 experiment, succeeded in discovering these particles in 1983, leading to the 1984 Nobel Prize in Physics being awarded to Carlo Rubbia and Simon van der Meer. The UA2 experiment also observed the first evidence for jet production in hadron collisions in 1981, and was involved in the searches of the top quark and of supersymmetric particles. Pierre Darriulat was the spokesperson of UA2 from 1981 to 1986, followed by Luigi Di Lella from 1986 to 1990.

<span class="mw-page-title-main">Super Proton Synchrotron</span> Particle accelerator at CERN, Switzerland

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<span class="mw-page-title-main">LHCb experiment</span> Experiment at the Large Hadron Collider

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<span class="mw-page-title-main">Intersecting Storage Rings</span> Particle accelerator at CERN, Switzerland

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<span class="mw-page-title-main">DØ experiment</span> Particle physics research project (1983–2011)

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<span class="mw-page-title-main">NA61 experiment</span>

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<span class="mw-page-title-main">CERN Hadron Linacs</span> Group of particle accelerators

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<span class="mw-page-title-main">Search for the Higgs boson</span> Effort to prove or disprove the existence of particle

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<span class="mw-page-title-main">Future Circular Collider</span> Proposed particle accelerator

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<span class="mw-page-title-main">Super Proton–Antiproton Synchrotron</span> Particle accelerator at CERN

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<span class="mw-page-title-main">FASER experiment</span> 2022 particle physics experiment at the Large Hadron Collider at CERN

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References

  1. 1 2 "The Particle Adventure | How do we experiment with tiny particles? | Fixed-target experiments". particleadventure.org. Retrieved 2021-07-16.
  2. ↑ "Detectors, Fixed-Target | Encyclopedia.com". encyclopedia.com. Retrieved 2021-07-16.
  3. 1 2 3 "Fixed-target physics". ed.fnal.gov. Retrieved 2021-07-16.
  4. ↑ "Fixed target, striking physics". CERN Courier. 2019-03-11. Retrieved 2021-07-21.
  5. 1 2 3 "Fixed Target vs Collider Experiments (with discussion) | Matt Evans". mtdevans.com. Retrieved 2021-07-22.
  6. ↑ Lincoln, Don (2013-08-02). "Fixed-target vs. collider". News. Archived from the original on 2022-01-21. Retrieved 2021-07-20.
  7. ↑ "Fixed Target and Colliding Beam Accelerators". www.hep.ucl.ac.uk. Retrieved 2021-07-22.
  8. ↑ Lawhun, Sarah (11 April 2018). "Right on target". symmetry magazine. Retrieved 2021-07-22.
  9. ↑ "Chapter 4 Accelerators and collider experiments" (PDF).
  10. ↑ Brodsky, S.J.; Fleuret, F.; Hadjidakis, C.; Lansberg, J.P. (2013-01-01). "Physics opportunities of a fixed-target experiment using LHC beams". Physics Reports. 522 (4): 239–255. arXiv: 1202.6585 . Bibcode:2013PhR...522..239B. doi:10.1016/j.physrep.2012.10.001. ISSN   0370-1573. S2CID   53312294.
  11. ↑ Topilskaya, Nataliya; Kurepin, Alexey (2019). Bondarenko, S.; Burov, V.; Malakhov, A. (eds.). "Some proposed fixed target experiments with the LHC beams". EPJ Web of Conferences. 204: 03002. Bibcode:2019EPJWC.20403002T. doi: 10.1051/epjconf/201920403002 . ISSN   2100-014X.
  12. 1 2 Loginov, Andrey Borisovich (2006). Search for anomalous production of events with a high energy lepton and photon at the Tevatron (Thesis). arXiv: hep-ex/0703011 . doi:10.2172/900361. OSTI   900361.
  13. 1 2 3 "Physics at a Fixed-Target Experiment Using the LHC Beams". Hindawi. Retrieved 2021-07-24.
  14. 1 2 3 Trzeciak, B.; Da Silva, C.; Ferreiro, E. G.; Hadjidakis, C.; Kikola, D.; Lansberg, J. P.; Massacrier, L.; Seixas, J.; Uras, A.; Yang, Z. (September 2017). "Heavy-Ion Physics at a Fixed-Target Experiment Using the LHC Proton and Lead Beams (AFTER@LHC): Feasibility Studies for Quarkonium and Drell–Yan Production". Few-Body Systems. 58 (5): 148. arXiv: 1703.03726 . Bibcode:2017FBS....58..148T. doi:10.1007/s00601-017-1308-0. ISSN   0177-7963. S2CID   119054649.
  15. ↑ Gutierrez, Gaston; Reyes, Marco A. (2014-11-10). "Fixed target experiments at the Fermilab Tevatron". International Journal of Modern Physics A. 29 (28): 1446008. arXiv: 1409.8243 . Bibcode:2014IJMPA..2946008G. doi:10.1142/S0217751X14460087. ISSN   0217-751X. S2CID   118569968.
  16. ↑ Küchler, D.; O’Neil, M.; Scrivens, R.; Thomae, R. (February 2014). "Preparation of a primary argon beam for the CERN fixed target physics". Review of Scientific Instruments. 85 (2): 02A954. Bibcode:2014RScI...85bA954K. doi:10.1063/1.4854275. ISSN   0034-6748. PMID   24593533.
  17. ↑ "Experiments | CERN". home.cern. Retrieved 2021-07-24.
  18. ↑ Brodsky, S.J.; Fleuret, F.; Hadjidakis, C.; Lansberg, J.P. (January 2013). "Physics opportunities of a fixed-target experiment using LHC beams". Physics Reports. 522 (4): 239–255. arXiv: 1202.6585 . Bibcode:2013PhR...522..239B. doi:10.1016/j.physrep.2012.10.001. S2CID   53312294.
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