Collider Detector at Fermilab

There were two particle detectors located on the Tevatron at Fermilab: CDF and DØ. CDF predated DØ as the first detector on the Tevatron. CDF's origins trace back to 1976, when Fermilab established the Colliding Beams Department under the leadership of Jim Cronin. This department focused on the development of both the accelerator that would produce colliding particle beams and the detector that would analyze those collisions. When the lab dissolved this department at the end of 1977, it established the Colliding Detector Facility Department under the leadership of Alvin Tollestrup. In 1980, Roy Schwitters became associate head of CDF and KEK in Japan and the National Laboratory of Frascati in Italy joined the collaboration. The collaboration completed a conceptual design report for CDF in the summer of 1981, and construction on the collision hall began on July 1, 1982. The lab dedicated the CDF detector on October 11, 1985, and CDF observed the Tevatron's first proton-antiproton collisions on October 13, 1985.{{Cite book|last1=Hoddeson|first1=Lillian|url=https://www.worldcat.org/oclc/192045754|title=Fermilab : physics, the frontier, and megascience|last2=Kolb|first2=Adrienne|last3=Westfall|first3=Catherine|date=2008|publisher=University of Chicago Press|isbn=978-0-226-34623-6|location=Chicago|oclc=192045754}}

Over the years, two major updates were made to CDF. The first upgrade began in 1989 and the second began in 2001. Each upgrade was considered a "run". Run 0 was the run before any upgrades (1988–1989), Run I was after the first upgrade, and Run II was after the second upgrade. The upgrades for Run I included the addition of a silicon vertex detector (the first such detector to be installed in a hadron collider experiment),{{Cite book |last=Hartmann |first=Frank |title=Evolution of Silicon Sensor Technology in Particle Physics |publisher=Springer, Cham |year=2017 |isbn=978-3-319-64436-3 |pages=195–218 |chapter=CDF: The World’s Largest Silicon Detector in the 20th Century; the First Silicon Detector at a Hadron Collider |series=Springer Tracts in Modern Physics |volume=275 |doi=10.1007/978-3-319-64436-3_5 |chapter-url=https://link.springer.com/chapter/10.1007/978-3-319-64436-3_5 |archive-date=2022-03-29 |access-date=2022-03-29 |archive-url=https://web.archive.org/web/20220329213609/https://link.springer.com/chapter/10.1007/978-3-319-64436-3_5 |url-status=live }} improvements to the central muon system, the addition of a vertex tracking system, the addition of central preradiator chambers, and improvements to the readout electronics and computer systems.{{Cite journal |date=1992-07-03 |title=CDF upgraded for collider run |url=https://history.fnal.gov/criers/FN_1992_07_03.pdf |journal=Ferminews |volume=15 |issue=12 |pages=3, 9}} Run II included upgrades on the central tracking system, preshower detectors and extension on muon coverage."Brief Description of the CDF Detector in Run II." (2004): 1-2.

CDF took data until the Tevatron was shut down in 2011, but CDF scientists continue to analyze data collected by the experiment.{{Cite web |date=2011-09-30 |title=Tevatron shuts down, but analysis continues |url=https://news.fnal.gov/2011/09/tevatron-shuts-analysis-continues/ |access-date=2022-03-22 |website=Fermilab - News |language=en-US |archive-date=2022-01-27 |archive-url=https://web.archive.org/web/20220127015830/https://news.fnal.gov/2011/09/tevatron-shuts-analysis-continues/ |url-status=live }}

File:CDF Collaborators Group Photo 94-0374-04.jpg

One of CDF's most famous discoveries is the observation of the top quark in February 1995.Kilminster, Ben. "CDF "Results of the Week" in Fermilab Today." The Collider Detector at Fermilab. Collider Detector at Fermilab. 28 Apr. 2009 . The existence of the top quark was hypothesized after the observation of the Upsilon at Fermilab in 1977, which was found to consist of a bottom quark and an anti-bottom quark. The Standard Model, the most widely accepted theory describing particles and their interactions, predicted the existence of three generations of quarks.{{cite web |url=https://home.cern/science/physics/standard-model |title=The Standard Model |author= |website=CERN |publisher=CERN |access-date=2019-05-28 |archive-date=2019-05-27 |archive-url=https://web.archive.org/web/20190527225210/https://home.cern/science/physics/standard-model |url-status=live }} The first generation quarks are the up and down quarks, second generation quarks are strange and charm, and third generation are top and bottom. The existence of the bottom quark solidified physicists' conviction that the top quark existed.Lankford, Andy. "Discovery of the Top Quark." Collider Detector at Fermilab. 25 Apr. 2009 . The top quark was the last of the quarks to be observed, mostly due to its comparatively high mass. Whereas the masses of the other quarks range from .005 GeV (up quark) to 4.7GeV (bottom quark), the top quark has a mass of 175 GeV."Quark Chart." The Particle Adventure. Particle Data Group. 5 May 2009 . Only Fermilab's Tevatron had the energy capability to produce and detect top anti-top pairs. The large mass of the top quark caused the top quark to decay almost instantaneously, within the order of 10⁻²⁵ seconds, making it extremely difficult to observe. The Standard Model predicts that the top quark may decay leptonically into a bottom quark and a W boson. This W boson may then decay into a lepton and neutrino (t→Wb→ѵlb). Therefore, CDF worked to reconstruct top events, looking specifically for evidence of bottom quarks, W bosons neutrinos. Finally in February 1995, CDF had enough evidence to say that they had "discovered" the top quark.Quigg, Chris. "Discovery of the Top Quark." 1996. Fermi National Accelerator Laboratory. 8 May 2009 . On February 24, CDF and DØ experimenters simultaneously submitted papers to Physical Review Letters describing the observation of the top quark. The two collaborations announced the discovery publicly at a seminar at Fermilab on March 2 and the papers were published on April 3.{{Cite journal |last1=Denisov |first1=Dmitri |last2=Vellidis |first2=Costas |date=2015-04-01 |title=The top quark, 20 years after its discovery |journal=Physics Today |volume=68 |issue=4 |pages=46–52 |doi=10.1063/PT.3.2749 |issn=0031-9228|doi-access=free }}

In 2019, the European Physical Society awarded the 2019 European Physical Society High Energy and Particle Physics Prize to the CDF and DØ collaborations "for the discovery of the top quark and the detailed measurement of its properties."{{Cite web |last=Hesla |first=Leah |date=2019-05-21 |title=European Physical Society gives top prize to Fermilab's CDF, DZero experiments for top quark discovery, measurements |url=https://news.fnal.gov/2019/05/european-physical-society-gives-top-prize-to-fermilabs-cdf-dzero-experiments-for-top-quark-discovery-measurements/ |access-date=2022-03-29 |website=Fermilab - News |language=en-US}}

On September 25, 2006, the CDF collaboration announced that they had discovered that the B-sub-s meson rapidly oscillates between matter and antimatter at a rate of 3 trillion times per second, a phenomenon called B–Bbar oscillation.{{Cite web |date=2006-09-25 |title=Fermilab's CDF scientists make it official: They have discovered the quick-change behavior of the B-sub-s meson, which switches between matter and antimatter 3 trillion times a second |url=https://news.fnal.gov/2006/09/fermilabs-cdf-scientists-make-official-discovered-quick-change-behavior-b-sub-s-meson-switches-matter-antimatter-3-trillion-times-second/ |access-date=2022-03-22 |website=Fermilab - News |language=en-US}}

On January 8, 2007, the CDF collaboration announced that they had achieved the world's most precise measurement by a single experiment of the mass of the W boson. This provided new constraints on the possible mass of the then-undiscovered Higgs boson.{{Cite web |date=2007-01-08 |title=CDF precision measurement of W-boson mass suggests a lighter Higgs particle |url=https://news.fnal.gov/2007/01/cdf-precision-measurement-w-boson-mass-suggests-lighter-higgs-particle/ |access-date=2022-03-22 |website=Fermilab - News |language=en-US |archive-date=2022-03-22 |archive-url=https://web.archive.org/web/20220322215554/https://news.fnal.gov/2007/01/cdf-precision-measurement-w-boson-mass-suggests-lighter-higgs-particle/ |url-status=live }}{{Cite web |title=Precision measurement of W-boson mass suggests a lighter Higgs particle |url=https://phys.org/news/2007-01-precision-w-boson-mass-lighter-higgs.html |access-date=2022-03-22 |website=phys.org |language=en}}

On April 7, 2022, the CDF collaboration announced in a paper published in the journal Science that they had made the most precise measurement ever of the mass of the W boson and found its actual mass to be significantly higher than the mass predicted by the Standard Model and the masses that had been measured before.{{Cite journal |last1=CDF Collaboration†‡ |last2=Aaltonen |first2=T. |last3=Amerio |first3=S. |last4=Amidei |first4=D. |last5=Anastassov |first5=A. |last6=Annovi |first6=A. |last7=Antos |first7=J. |last8=Apollinari |first8=G. |last9=Appel |first9=J. A. |last10=Arisawa |first10=T. |last11=Artikov |first11=A. |date=2022-04-08 |title=High-precision measurement of the W boson mass with the CDF II detector |url=https://www.science.org/doi/10.1126/science.abk1781 |journal=Science |language=en |volume=376 |issue=6589 |pages=170–176 |doi=10.1126/science.abk1781 |pmid=35389814 |issn=0036-8075 |hdl=11390/1225696 |s2cid=248025265 |hdl-access=free |archive-date=2022-04-13 |access-date=2022-04-07 |archive-url=https://web.archive.org/web/20220413142608/https://www.science.org/doi/10.1126/science.abk1781 |url-status=live }} In 2023, the ATLAS experiment at the Large Hadron Collider released an improved measurement for the mass of the W boson, 80,360 ± 16 MeV, which aligned with predictions from the Standard Model.{{cite web |last1=Ouellette |first1=Jennifer |date=24 March 2023 |title=New value for W boson mass dims 2022 hints of physics beyond Standard Model |url=https://arstechnica.com/science/2023/03/new-value-for-w-boson-mass-dims-2022-hints-of-physics-beyond-standard-model/ |access-date=26 March 2023 |website=Ars Technica |language=en-us |archive-date=11 May 2023 |archive-url=https://web.archive.org/web/20230511233918/https://arstechnica.com/science/2023/03/new-value-for-w-boson-mass-dims-2022-hints-of-physics-beyond-standard-model/ |url-status=live }}{{cite web |date=22 March 2023 |title=Improved W boson Mass Measurement using $\sqrt{s}=7$ TeV Proton-Proton Collisions with the ATLAS Detector |url=https://atlas.web.cern.ch/Atlas/GROUPS/PHYSICS/CONFNOTES/ATLAS-CONF-2023-004/ |access-date=26 March 2023 |website=ATLAS experiment |publisher=CERN}}

CDF scientists also discovered several other particles, including the B-sub-c meson{{Cite news |last=Jackson |first=Judy |date=1998-03-20 |title=CDF Corrals the Last of the Mesons |pages=1–2 |work=FermiNews |url=https://www.fnal.gov/pub/ferminews/FermiNews98-03-20.pdf |access-date=2022-03-29}} (announced March 5, 1998); sigma-sub-b baryons, baryons consisting of two up quarks and a bottom quark and of two down quarks and a bottom quark (announced October 23, 2006);{{Cite web |date=2006-10-23 |title=Experimenters at Fermilab discover exotic relatives of protons and neutrons |url=https://news.fnal.gov/2006/10/experimenters-fermilab-discover-exotic-relatives-protons-neutrons/ |access-date=2022-03-22 |website=Fermilab - News |language=en-US |archive-date=2022-03-22 |archive-url=https://web.archive.org/web/20220322215555/https://news.fnal.gov/2006/10/experimenters-fermilab-discover-exotic-relatives-protons-neutrons/ |url-status=live }} cascade-b baryons, consisting of a down, a strange, and a bottom quark (discovered jointly with DØ and announced on June 15, 2007);{{Cite web |date=2007-06-25 |title=Back-to-Back b Baryons in Batavia |url=https://news.fnal.gov/2007/06/back-back-b-baryons-batavia/ |access-date=2022-03-22 |website=Fermilab - News |language=en-US |archive-date=2022-03-22 |archive-url=https://web.archive.org/web/20220322215557/https://news.fnal.gov/2007/06/back-back-b-baryons-batavia/ |url-status=live }} and omega-sub-b baryons, consisting of two strange quarks and a bottom quark (announced in June 2009).{{Cite web |date=2009-06-29 |title=Fermilab's CDF observes Omega-sub-b baryon |url=https://news.fnal.gov/2009/06/fermilabs-cdf-observes-omega-sub-b-baryon/ |access-date=2022-03-22 |website=Fermilab - News |language=en-US}}

In order for physicists to understand the data corresponding to each event, they must understand the components of the CDF detector and how the detector works. Each component affects what the data will look like. Today, the 5000-ton detector sits in B0 and analyzes millions of beam collisions per second.Yoh, John (2005). Brief Introduction to the CDF Experiment. Retrieved April 28, 2008, Web site: http://www-cdf.fnal.gov/events/cdfintro.html {{Webarchive|url=https://web.archive.org/web/20090826143435/http://www-cdf.fnal.gov/events/cdfintro.html |date=2009-08-26 }}

The detector is designed in many different layers. Each of these layers work simultaneously with the other components of the detector in an effort to interact with the different particles, thereby giving physicists the opportunity to "see" and study the individual particles.

CDF can be divided into layers as follows:

• Layer 1: Beam Pipe
• Layer 2: Silicon Detector
• Layer 3: Central Outer Tracker
• Layer 4: Solenoid Magnet
• Layer 5: Electromagnetic Calorimeters
• Layer 6: Hadronic Calorimeters
• Layer 7: Muon Detectors

The beam pipe is the innermost layer of CDF. The beam pipe is where the protons and anti-protons, traveling at approximately 0.99996 c, collide head on. Each of the protons is moving extremely close to the speed of light with extremely high energies. In a collision, much of the energy is converted into mass. This allows proton/anti-proton annihilation to produce daughter particles, such as top quarks with a mass of 175 GeV, much heavier than the original protons.Lee, Jenny (2008). The Collider Detector at Fermilab. Retrieved September 26, 2008, from CDF Virtual Tour Web site: http://www-cdf.fnal.gov/ {{Webarchive|url=https://web.archive.org/web/20180520174340/https://www-cdf.fnal.gov/ |date=2018-05-20 }}

File:Collider Detector at Fermilab (CDF) silicon vertex detector.JPG

File:Collider Detector at Fermilab (CDF) silicon vertex detector cross section.JPG

Surrounding the beam pipe is the silicon detector. This detector is used to track the path of charged particles as they travel through the detector. The silicon detector begins at a radius of r = 1.5 cm from the beam line and extends to a radius of r = 28 cm from the beam line. The silicon detector is composed of seven layers of silicon arranged in a barrel shape around the beam pipe. Silicon is often used in charged particle detectors because of its high sensitivity, allowing for high-resolution vertex and tracking."Particle Detectors." Particle Data Group. 24 July 2008. Fermi National Accelerator Laboratory. 11 May 2009 . The first layer of silicon, known as Layer 00, is a single sided detector designed to separate signal from background even under extreme radiation. The remaining layers are double sided and radiation-hard, meaning that the layers are protected from damage from radioactivity. The silicon works to track the paths of charged particles as they pass through the detector by ionizing the silicon. The density of the silicon, coupled with the low ionization energy of silicon, allow ionization signals to travel quickly. As a particle travels through the silicon, its position will be recorded in 3 dimensions. The silicon detector has a track hit resolution of 10 μm, and impact parameter resolution of 30 μm. Physicists can look at this trail of ions and determine the path that the particle took. As the silicon detector is located within a magnetic field, the curvature of the path through the silicon allows physicists to calculate the momentum of the particle. More curvature means less momentum and vice versa.

Outside of the silicon detector, the central outer tracker works in much the manner as the silicon detector as it is also used to track the paths of charged particles and is also located within a magnetic field. The COT, however, is not made of silicon. Silicon is tremendously expensive and is not practical to purchase in extreme quantities. COT is a gas chamber filled with tens of thousands of gold wires arranged in layers and argon gas. Two types of wires are used in the COT: sense wires and field wires. Sense wires are thinner and attract the electrons that are released by the argon gas as it is ionized. The field wires are thicker than the sense wires and attract the positive ions formed from the release of electrons. There are 96 layers of wire and each wire is placed approximately 3.86 mm apart from one another. As in the silicon detector, when a charged particle passes through the chamber it ionizes the gas. This signal is then carried to a nearby wire, which is then carried to the computers for read-out. The COT is approximately 3.1 m long and extends from r = 40 cm to r = 137 cm. Although the COT is not nearly as precise as the silicon detector, the COT has a hit position resolution of 140 μm and a momentum resolution of 0.0015 (GeV/c)⁻¹.

The solenoid magnet surrounds both the COT and the silicon detector. The purpose of the solenoid is to bend the trajectory of charged particles in the COT and silicon detector by creating a magnetic field parallel to the beam. The solenoid has a radius of r = 1.5 m and is 4.8 m in length. The curvature of the trajectory of the particles in the magnet field allows physicists to calculate the momentum of each of the particles. The higher the curvature, the lower the momentum and vice versa. Because the particles have such a high energy, a very strong magnet is needed to bend the paths of the particles. The solenoid is a superconducting magnet cooled by liquid helium. The helium lowers the temperature of the magnet to 4.7 K or −268.45 °C which reduces the resistance to almost zero, allowing the magnet to conduct high currents with minimal heating and very high efficiency, and creating a powerful magnetic field.

Calorimeters quantify the total energy of the particles by converting the energy of particles to visible light though polystyrene scintillators. CDF uses two types of calorimeters: electromagnetic calorimeters and hadronic calorimeters. The electromagnetic calorimeter measures the energy of light particles and the hadronic calorimeter measures the energy of hadrons. The central electromagnetic calorimeter uses alternating sheets of lead and scintillator. Each layer of lead is approximately {{convert|3/4|in|mm|sigfig=1|abbr=on|disp=flip}} wide. The lead is used to stop the particles as they pass through the calorimeter and the scintillator is used to quantify the energy of the particles. The hadronic calorimeter works in much the same way except the hadronic calorimeter uses steel in place of lead. Each calorimeter forms a wedge, which consists of both an electromagnetic calorimeter and a hadronic calorimeter. These wedges are about {{convert|8|ft|m|abbr=on|disp=flip}} in length and are arranged around the solenoid.

The final "layer" of the detector consists of the muon detectors. Muons are charged particles that may be produced when heavy particles decay. These high-energy particles hardly interact so the muon detectors are strategically placed at the farthest layer from the beam pipe behind large walls of steel. The steel ensures that only extremely high-energy particles, such as neutrinos and muons, pass through to the muon chambers. There are two aspects of the muon detectors: the planar drift chambers and scintillators. There are four layers of planar drift chambers, each with the capability of detecting muons with a transverse momentum p_T > 1.4 GeV/c. These drift chambers work in the same way as the COT. They are filled with gas and wire. The charged muons ionize the gas and the signal is carried to readout by the wires.

Understanding the different components of the detector is important because the detector determines what data will look like and what signal one can expect to see for each particle. A detector is basically a set of obstacles used to force particles to interact, allowing physicists to "see" the presence of a certain particle. If a charged quark is passing through the detector, the evidence of this quark will be a curved trajectory in the silicon detector and COT deposited energy in the calorimeter. If a neutral particle, such as a neutron, passes through the detector, there will be no track in the COT and silicon detector but deposited energy in the hadronic calorimeter. Muons may appear in the COT and silicon detector and as deposited energy in the muon detectors. Likewise, a neutrino, which rarely if ever interacts, will express itself only in the form of missing energy.

{{Reflist}}

• Worlds within the atom, National Geographic article, May, 1985

• [http://www.fnal.gov/pub/ferminews/ferminews01-05-04/p2.html Fermilab news page]
• [https://cdf.fnal.gov/ The Collider Detector At Fermilab (CDF)]
• Record of [https://inspirehep.net/experiments/1110316 CDF] experiment on INSPIRE-HEP

Category:Particle experiments

Category:Fermilab

Category:Fermilab experiments