Fixed-target experiment

The energy involved in a fixed target experiment is 4 times smaller compared to that in collider with the dual beams of same energy.{{Cite web|title=Fixed Target vs Collider Experiments (with discussion) {{!}} Matt Evans|url=https://mtdevans.com/projects/physics-problems/fixed-target-vs-collider-experiments-with-discussion/index.html|access-date=2021-07-22|website=mtdevans.com}}{{Cite web|last=Lincoln|first=Don|date=2013-08-02|title=Fixed-target vs. collider|url=https://news.fnal.gov/2013/08/fixed-target-vs-collider/|access-date=2021-07-20|website=News|language=en-US|archive-date=2022-01-21|archive-url=https://web.archive.org/web/20220121054434/https://news.fnal.gov/2013/08/fixed-target-vs-collider/|url-status=dead}} 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.{{Cite web|title=Fixed Target and Colliding Beam Accelerators|url=https://www.hep.ucl.ac.uk/undergrad-projects/3rdyear/PPguide/ftcba.htm|access-date=2021-07-22|website=www.hep.ucl.ac.uk}} 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.{{Cite web|last=Lawhun|first=Sarah|title=Right on target|url=https://www.symmetrymagazine.org/article/right-on-target|access-date=2021-07-22|website=symmetry magazine|date=11 April 2018 |language=en}}

The fixed target experiments have a significant advantage for experiments that require higher luminosity (rate of interaction).{{Cite web |title=Chapter 4 Accelerators and collider experiments |url=https://edu.itp.phys.ethz.ch/hs10/ppp1/PPP1_4.pdf }} 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 $\backslash mathrm\{5\; \backslash times\; 10^\{35\}\; cm^\{-2\}\; s^\{-1\}\}$ in its run.{{Cite journal|date=2013-01-01|title=Physics opportunities of a fixed-target experiment using LHC beams|url=https://www.sciencedirect.com/science/article/abs/pii/S0370157312003468|journal=Physics Reports|language=en|volume=522|issue=4|pages=239–255|doi=10.1016/j.physrep.2012.10.001|issn=0370-1573|last1=Brodsky|first1=S.J.|last2=Fleuret|first2=F.|last3=Hadjidakis|first3=C.|last4=Lansberg|first4=J.P.|arxiv=1202.6585|bibcode=2013PhR...522..239B|s2cid=53312294}} While luminosity scale of about $\backslash mathrm\{5\; \backslash times\; 10^\{34\}\; cm^\{-2\}\; s^\{-1\}\}$ have already been approached by older fixed target experiments such at the E288 led by Leon Lederman at Fermilab.{{Cite journal|last1=Topilskaya|first1=Nataliya|last2=Kurepin|first2=Alexey|date=2019|editor-last=Bondarenko|editor-first=S.|editor2-last=Burov|editor2-first=V.|editor3-last=Malakhov|editor3-first=A.|title=Some proposed fixed target experiments with the LHC beams|journal=EPJ Web of Conferences|volume=204|pages=03002|doi=10.1051/epjconf/201920403002|bibcode=2019EPJWC.20403002T|issn=2100-014X|doi-access=free}} Another advantage for fixed-target experiments is that they are easier and cheaper to build compared to the collider accelerators.

File:Fte111.jpg 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.{{Cite thesis|last=Loginov|first=Andrey Borisovich|title=Search for anomalous production of events with a high energy lepton and photon at the Tevatron|date=2006|url=https://www.osti.gov/biblio/900361/|doi=10.2172/900361|osti=900361|degree=|arxiv=hep-ex/0703011}} 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.{{Cite web|title=Physics at a Fixed-Target Experiment Using the LHC Beams|url=https://www.hindawi.com/journals/ahep/si/354953/|access-date=2021-07-24|website=Hindawi|language=en}}{{Cite journal|last1=Trzeciak|first1=B.|last2=Da Silva|first2=C.|last3=Ferreiro|first3=E. G.|last4=Hadjidakis|first4=C.|last5=Kikola|first5=D.|last6=Lansberg|first6=J. P.|last7=Massacrier|first7=L.|last8=Seixas|first8=J.|last9=Uras|first9=A.|last10=Yang|first10=Z.|date=September 2017|title=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|url=http://link.springer.com/10.1007/s00601-017-1308-0|journal=Few-Body Systems|language=en|volume=58|issue=5|pages=148|doi=10.1007/s00601-017-1308-0|arxiv=1703.03726|bibcode=2017FBS....58..148T|s2cid=119054649|issn=0177-7963}}

File:Fte222.jpg 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.

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.{{Cite journal|last1=Gutierrez|first1=Gaston|last2=Reyes|first2=Marco A.|date=2014-11-10|title=Fixed target experiments at the Fermilab Tevatron|url=https://www.worldscientific.com/doi/abs/10.1142/S0217751X14460087|journal=International Journal of Modern Physics A|language=en|volume=29|issue=28|pages=1446008|doi=10.1142/S0217751X14460087|arxiv=1409.8243|bibcode=2014IJMPA..2946008G|s2cid=118569968|issn=0217-751X}}

NA61/SHINE at the SPS is studying the phase transitions in strongly interacting matter and physics related to onset of confinement.{{Cite journal|last1=Küchler|first1=D.|last2=O’Neil|first2=M.|last3=Scrivens|first3=R.|last4=Thomae|first4=R.|date=February 2014|title=Preparation of a primary argon beam for the CERN fixed target physics|url=http://aip.scitation.org/doi/10.1063/1.4854275|journal=Review of Scientific Instruments|language=en|volume=85|issue=2|pages=02A954|doi=10.1063/1.4854275|pmid=24593533|bibcode=2014RScI...85bA954K|issn=0034-6748|url-access=subscription}} While the COMPASS experiment investigates the structure of the hadrons.{{Cite web|title=Experiments {{!}} CERN|url=https://home.cern/science/experiments|access-date=2021-07-24|website=home.cern}}

AFTER@LHC aims at the studies of gluon and quark distribution inside protons and neutrons using fixed-target facilities. There are possibilities to observe the W and Z bosons as well.{{Cite journal|last1=Brodsky|first1=S.J.|last2=Fleuret|first2=F.|last3=Hadjidakis|first3=C.|last4=Lansberg|first4=J.P.|date=January 2013|title=Physics opportunities of a fixed-target experiment using LHC beams|url=https://linkinghub.elsevier.com/retrieve/pii/S0370157312003468|journal=Physics Reports|language=en|volume=522|issue=4|pages=239–255|doi=10.1016/j.physrep.2012.10.001|arxiv=1202.6585|bibcode=2013PhR...522..239B|s2cid=53312294}} Observation and studies of the Drell-Yan pair production and quarkonium are also being looked into.

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

• Collider
• List of fixed-target experiments

• [https://home.cern/science/experiments Fixed-target experiments at CERN]

{{Reflist}}

Category:Experimental particle physics

Category:Particle experiments

Category:Fixed-target experiments