View source for LHCf experiment

{{LHC}}

The '''LHCf''' ('''Large Hadron Collider forward''') is a special-purpose [[Large Hadron Collider]] experiment for astroparticle ([[cosmic ray]]) physics, and one of nine detectors in the LHC accelerator at [[CERN]]. LHCf is designed to study the particles generated in the [[Pseudorapidity|forward]] region of collisions, those almost directly in line with the colliding proton beams.<ref>{{Cite web |date=2023-07-21 |title=LHCf |url=https://home.cern/science/experiments/lhcf |access-date=2023-08-07 |website=CERN |language=en}}</ref>
[[File:LHCf_experiment.jpg|thumb|The LHCf experiment in the LHC tunnel]]

==Purpose==
The LHCf is intended to measure the energy and numbers of neutral [[pions]] ({{Subatomic particle|Pion0}}) produced by the collider. This will hopefully help explain the origin of [[ultra-high-energy cosmic ray]]s (UHECRs).<ref>{{Cite journal |last1=LHCf Collaboration |last2=Adriani |first2=O. |last3=Berti |first3=E. |last4=Bonechi |first4=L. |last5=Bongi |first5=M. |last6=D’Alessandro |first6=R. |last7=Del Prete |first7=M. |last8=Haguenauer |first8=M. |last9=Itow |first9=Y. |last10=Iwata |first10=T. |last11=Kasahara |first11=K. |last12=Kawade |first12=K. |last13=Makino |first13=Y. |last14=Masuda |first14=K. |last15=Matsubayashi |first15=E. |date=2016-08-22 |title=Measurements of longitudinal and transverse momentum distributions for neutral pions in the forward-rapidity region with the LHCf detector |url=https://link.aps.org/doi/10.1103/PhysRevD.94.032007 |journal=Physical Review D |volume=94 |issue=3 |pages=032007 |doi=10.1103/PhysRevD.94.032007|arxiv=1507.08764 |bibcode=2016PhRvD..94c2007A |s2cid=111375019 }}</ref><ref name=":0">{{Cite book |last1=Tiberio |first1=Alessio |last2=Adriani |first2=O. |last3=Berti |first3=E. |last4=Betti |first4=P. |last5=Bonechi |first5=L. |last6=Bongi |first6=M. |last7=D'Alessandro |first7=R. |last8=Haguenauer |first8=M. |last9=Itow |first9=Y. |last10=Kasahara |first10=K. |last11=Kondo |first11=M. |last12=Matsubara |first12=Y. |last13=Menjo |first13=H. |last14=Muraki |first14=Y. |last15=Ohashi |first15=K. |title=Proceedings of 38th International Cosmic Ray Conference |chapter=The LHCF experiment at the Large Hadron Collider: Status and prospects |date=2023-07-25 |language=en |pages=444 |doi=10.22323/1.444.0444|doi-access=free }}</ref> Detecting UHECRs is performed through observations of secondary [[Particle shower|particle showers]] produced when a UHECR interacts with the atmosphere. The LHCf experiment is designed to measure the very-forward region, where most of the energy flow of secondary particles is contained.<ref name=":0" />

The results produced by the LHCf experiment complement other high-energy cosmic ray measurements from the [[Pierre Auger Observatory]] in Argentina, and the [[Telescope Array Project]] in Utah.<ref>{{Cite journal |last1=Noda |first1=K |last2=Adriani |first2=O |last3=Bonechi |first3=L |last4=Bongi |first4=M |last5=Castellini |first5=G |display-authors=4 |date=Sep 2011 |title=The LHCf experiment |url=https://pos.sissa.it/148/066/pdf |journal=VI European Summer School on Experimental Nuclear Astrophysics}}</ref><ref>{{Cite web |date=2015-03-03 |title=What is LHCf? |url=http://www.uslhc.us/What_is_the_LHC/Experiments/LHCf |access-date=2023-08-08 |website=US/LHC|archive-url=https://web.archive.org/web/20150303123247/http://www.uslhc.us/What_is_the_LHC/Experiments/LHCf |archive-date=2015-03-03 }}</ref>

== Experimental setup ==
The LHCf setup consists of two independent detectors on either side of the LHC, both 140 m from the [[ATLAS experiment|ATLAS]] interaction point.<ref>{{Cite web |date=2006-11-01 |title=LHCf: a tiny new experiment joins the LHC |url=https://cerncourier.com/a/lhcf-a-tiny-new-experiment-joins-the-lhc/ |access-date=2023-08-07 |website=CERN Courier |language=en-GB}}</ref><ref>{{Cite web |last=Adriani |first=Oscar |date=9 Sep 2005 |title=The LHCf experiment at LHC |url=http://www.particle.cz/conferences/c2cr2005/talks/Adriani.pdf |access-date=7 Aug 2023}}</ref> The detectors are referred to as Arm 1 and Arm 2 and are installed inside target neutral absorbers (TAN), which protect cryo-magnets from neutral particle debris from the interaction region.<ref>{{Cite journal |last1=Collaboration |first1=The LHCf |last2=Adriani |first2=O |last3=Bonechi |first3=L |last4=Bongi |first4=M |last5=Castellini |first5=G |last6=D'Alessandro |first6=R |last7=Faus |first7=D A |last8=Fukui |first8=K |last9=Grandi |first9=M |last10=Haguenauer |first10=M |last11=Itow |first11=Y |last12=Kasahara |first12=K |last13=Macina |first13=D |last14=Mase |first14=T |last15=Masuda |first15=K |date=2008-08-14 |title=The LHCf detector at the CERN Large Hadron Collider |journal=Journal of Instrumentation |volume=3 |issue=8 |pages=S08006 |doi=10.1088/1748-0221/3/08/S08006 |bibcode=2008JInst...3S8006L |s2cid=250679205 |issn=1748-0221|doi-access=free |hdl=10550/42770 |hdl-access=free }}</ref><ref>{{Cite book |last=Piparo |first=Giuseppe |title=Proceedings of 38th International Cosmic Ray Conference |chapter=Measurement of the very forward π0 and η meson productions in p-p collisions at √s=13 TeV with the LHCF detector |date=2023-07-25  |language=en |pages=447 |doi=10.22323/1.444.0447|doi-access=free }}</ref><ref>{{Cite journal |last1=Adriani |first1=O. |last2=Bonechi |first2=L. |last3=Bongi |first3=M. |last4=Castellini |first4=G. |last5=D'alessandro |first5=R. |last6=Haguenauer |first6=M. |last7=Iso |first7=T. |last8=Itow |first8=Y. |last9=Kasahara |first9=K. |last10=Kawade |first10=K. |last11=Masuda |first11=K. |last12=Menjo |first12=H. |last13=Mitsuka |first13=G. |last14=Muraki |first14=Y. |last15=Noda |first15=K. |date=2013-10-10 |title=LHCf DETECTOR PERFORMANCE DURING THE 2009–2010 LHC RUN |url=https://www.worldscientific.com/doi/abs/10.1142/S0217751X13300366 |journal=International Journal of Modern Physics A |volume=28 |issue=25 |pages=1330036 |doi=10.1142/S0217751X13300366 |bibcode=2013IJMPA..2830036A |issn=0217-751X}}</ref>

The two detectors have a common structure of two independent [[Calorimeter (particle physics)|calorimeter]] towers, for [[photon]] and [[neutron]] measurements. The towers are made from [[tungsten]] absorber layers and [[scintillator]] layers, with a difference in the size of transverse sections for the two arms.<ref>{{Cite journal |last1=Makino |first1=Y. |last2=Tiberio |first2=A. |last3=Adriani |first3=O. |last4=Berti |first4=E. |last5=Bonechi |first5=L. |last6=Bongi |first6=M. |last7=Caccia |first7=Z. |last8=D'Alessandro |first8=R. |last9=Prete |first9=M. Del |last10=Detti |first10=S. |last11=Haguenauer |first11=M. |last12=Itow |first12=Y. |last13=Iwata |first13=T. |last14=Kasahara |first14=K. |last15=Masuda |first15=K. |date=2017-03-21 |title=Performance study for the photon measurements of the upgraded LHCf calorimeters with Gd 2 SiO 5 (GSO) scintillators |url=https://iopscience.iop.org/article/10.1088/1748-0221/12/03/P03023 |journal=Journal of Instrumentation |volume=12 |issue=3 |pages=P03023 |doi=10.1088/1748-0221/12/03/P03023 |bibcode=2017JInst..12P3023M |s2cid=125806123 |issn=1748-0221}}</ref> The calorimeter towers are used to measure incoming particle energy and to identify families of particles. Each detector has a tracking system: the Arm 1 system consists of four double-layers os scintillating fibres; Arm 2 consists of [[microstrip]] silicon layers.<ref>{{Cite journal |last=Bonechi |first=Lorenzo |date=2008-03-01 |title=LHCf: a LHC Detector for Astroparticle Physics |url=https://www.sciencedirect.com/science/article/pii/S0920563207009516 |journal=Nuclear Physics B - Proceedings Supplements |series=Proceedings of the Hadron Collider Physics Symposium 2007 |language=en |volume=177-178 |pages=263–264 |doi=10.1016/j.nuclphysbps.2007.11.122 |bibcode=2008NuPhS.177..263B |issn=0920-5632|hdl=10261/9064 |hdl-access=free }}</ref> The energy resolution for the detectors is over 3% for photons above 100 GeV and around 40% for neutrons.<ref name=":1">{{Cite journal |last1=Makino |first1=Y. |last2=Tiberio |first2=A. |last3=Adriani |first3=O. |last4=Berti |first4=E. |last5=Bonechi |first5=L. |last6=Bongi |first6=M. |last7=Caccia |first7=Z. |last8=D'Alessandro |first8=R. |last9=Prete |first9=M. Del |last10=Detti |first10=S. |last11=Haguenauer |first11=M. |last12=Itow |first12=Y. |last13=Iwata |first13=T. |last14=Kasahara |first14=K. |last15=Masuda |first15=K. |date=2017-03-21 |title=Performance study for the photon measurements of the upgraded LHCf calorimeters with Gd 2 SiO 5 (GSO) scintillators |url=https://iopscience.iop.org/article/10.1088/1748-0221/12/03/P03023 |journal=Journal of Instrumentation |volume=12 |issue=3 |pages=P03023 |doi=10.1088/1748-0221/12/03/P03023 |bibcode=2017JInst..12P3023M |s2cid=125806123 |issn=1748-0221}}</ref><ref name=":0" /> The position resolution for Arm 1 and Arm 2 is 200 μm and 40 μm for photons respectively, and is around 1 mm for neutrons for both the detectors.<ref name=":1" /><ref>{{Cite journal |last1=Adriani |first1=O |last2=Bonechi |first2=L |last3=Bongi |first3=M |last4=Castellini |first4=G |last5=Ciaranfi |first5=R |last6=D'Alessandro |first6=R |last7=Grandi |first7=M |last8=Papini |first8=P |last9=Ricciarini |first9=S |last10=Tricomi |first10=A |last11=Viciani |first11=A |date=2010-01-26 |title=The construction and testing of the silicon position sensitive modules for the LHCf experiment at CERN |url=https://iopscience.iop.org/article/10.1088/1748-0221/5/01/P01012 |journal=Journal of Instrumentation |volume=5 |issue=1 |pages=P01012 |doi=10.1088/1748-0221/5/01/P01012 |bibcode=2010JInst...5.1012A |s2cid=250686091 |issn=1748-0221}}</ref><ref name=":0" />

== Results ==
The first phase of data using the LHCf detectors was recorded in 2009-2013, as part of the LHC's Run 1.<ref>{{Cite web |date=2023-07-21 |title=LHC report: Run 1 - the final flurry |url=https://home.cern/news/news/accelerators/lhc-report-run-1-final-flurry |access-date=2023-08-08 |website=CERN |language=en}}</ref> The LHCf results at 7 TeV centre-of-mass energy showed good agreement with theoretical models for forward photon and neutral pion production. However, the results did not agree for the forward neutron production.<ref>{{Cite web |date=2023-07-21 |title=Smaller LHC collaborations to analyse collisions at 13 TeV |url=https://home.cern/news/news/accelerators/smaller-lhc-collaborations-analyse-collisions-13-tev |access-date=2023-08-08 |website=CERN |language=en}}</ref><ref>{{Cite journal |last1=Adriani |first1=O. |last2=Berti |first2=E. |last3=Bonechi |first3=L. |last4=Bongi |first4=M. |last5=Castellini |first5=G. |last6=D'Alessandro |first6=R. |last7=Del Prete |first7=M. |last8=Haguenauer |first8=M. |last9=Itow |first9=Y. |last10=Kasahara |first10=K. |last11=Kawade |first11=K. |last12=Makino |first12=Y. |last13=Masuda |first13=K. |last14=Matsubayashi |first14=E. |last15=Menjo |first15=H. |date=Nov 2015 |title=Measurement of very forward neutron energy spectra for 7 TeV proton--proton collisions at the Large Hadron Collider |journal=Physics Letters B |volume=750 |pages=360–366 |doi=10.1016/j.physletb.2015.09.041|arxiv=1503.03505 |bibcode=2015PhLB..750..360A |s2cid=118480688 }}</ref>

LHCf was able to measure how the number of forward photons and neutrons varies with energy at new high energies. The results of the experiment agree with some theoretical models but disagree with other.<ref>{{Cite web |date=2023-07-21 |title=LHCf gears up to probe birth of cosmic-ray showers |url=https://home.cern/news/news/experiments/lhcf-gears-probe-birth-cosmic-ray-showers |access-date=2023-08-08 |website=CERN |language=en}}</ref><ref>{{Cite journal |last1=Adriani |first1=O. |last2=Berti |first2=E. |last3=Bonechi |first3=L. |last4=Bongi |first4=M. |last5=D'Alessandro |first5=R. |last6=Haguenauer |first6=M. |last7=Itow |first7=Y. |last8=Iwata |first8=T. |last9=Kasahara |first9=K. |last10=Makino |first10=Y. |last11=Masuda |first11=K. |last12=Matsubayashi |first12=E. |last13=Menjo |first13=H. |last14=Muraki |first14=Y. |last15=Papini |first15=P. |date=2018-05-10 |title=Measurement of forward photon production cross-section in proton–proton collisions at {{sqrt|s}} = 13TeV with the LHCf detector |journal=Physics Letters B |language=en |volume=780 |pages=233–239 |doi=10.1016/j.physletb.2017.12.050 |s2cid=53972544 |issn=0370-2693|doi-access=free |arxiv=1703.07678 }}</ref><ref>{{Cite journal |last1=Adriani |first1=O. |last2=Berti |first2=E. |last3=Bonechi |first3=L. |last4=Bongi |first4=M. |last5=D’Alessandro |first5=R. |last6=Detti |first6=S. |last7=Haguenauer |first7=M. |last8=Itow |first8=Y. |last9=Kasahara |first9=K. |last10=Makino |first10=Y. |last11=Masuda |first11=K. |last12=Menjo |first12=H. |last13=Muraki |first13=Y. |last14=Ohashi |first14=K. |last15=Papini |first15=P. |date=2018-11-12 |title=Measurement of inclusive forward neutron production cross section in proton-proton collisions at {{sqrt|s}} = 13 TeV with the LHCf Arm2 detector |journal=Journal of High Energy Physics |language=en |volume=2018 |issue=11 |pages=73 |doi=10.1007/JHEP11(2018)073 |s2cid=256045598 |issn=1029-8479|doi-access=free |arxiv=1808.09877 }}</ref>

The current focus of the LHCf is to look out for neutral kaons and neutral eta mesons, particles that include a strange quark. The theoretical models describing this interaction predict secondary muons, but the predicted numbers disagree with experimental data. The LHCf experiment hopes to resolve the "muon puzzle".<ref>{{Cite web |date=2023-07-21 |title=LHCf continues to investigate cosmic rays |url=https://home.cern/news/news/experiments/lhcf-continues-investigate-cosmic-rays |access-date=2023-08-08 |website=CERN |language=en}}</ref><ref>{{Cite journal |last1=Albrecht |first1=Johannes |last2=Cazon |first2=Lorenzo |last3=Dembinski |first3=Hans |last4=Fedynitch |first4=Anatoli |last5=Kampert |first5=Karl-Heinz |last6=Pierog |first6=Tanguy |last7=Rhode |first7=Wolfgang |last8=Soldin |first8=Dennis |last9=Spaan |first9=Bernhard |last10=Ulrich |first10=Ralf |last11=Unger |first11=Michael |date=2022-03-09 |title=The Muon Puzzle in cosmic-ray induced air showers and its connection to the Large Hadron Collider |url=https://doi.org/10.1007/s10509-022-04054-5 |journal=Astrophysics and Space Science |language=en |volume=367 |issue=3 |pages=27 |doi=10.1007/s10509-022-04054-5 |arxiv=2105.06148 |bibcode=2022Ap&SS.367...27A |s2cid=234482981 |issn=1572-946X}}</ref>

==External links==
*{{Commons category-inline}}
* [https://inspirehep.net/experiments/1126263 LHCf experiment]  record on [[INSPIRE-HEP]]

== References ==
<references />
{{CERN}}
[[Category:CERN experiments]]
[[Category:Particle experiments]]
[[Category:Large Hadron Collider]]
{{coord|46|14|09|N|6|03|18|E|region:CH-GE_type:landmark_source:kolossus-dewiki|display=title}}{{particle-stub}}