We discuss prospects of deep inelastic scattering physics capabilities at the
future muon collider facility. In addition to mu^+ mu^- collider itself, the
facility provides other possibilities. Among the possibilities, we present
muon-proton collider and neutrino fixed target programs at the muon collider
facility. This mu-p collider program extends kinematic reach and luminosity by
an order of magnitude, increasing the possibility of search for new exotic
particles. Perhaps most intriguing DIS prospects come from utilizing high
intensity neutrino beam resulting from continuous decays of muons in various
sections of the muon collider facility. One of the most interesting findings is
a precision measurement of electroweak mixing angle, sin^2theta_W, which can be
achieved to the precision equivalent to delta M_W ~ 30 MeV.Comment: 8 pages, 4 figures, To be published in the proceedings of the 6th
  international workshop on Deep Inelastic Scattering, Brussel, Belgium (1998

Yu, J.

English

arXiv

We discuss prospects of deep inelastic scattering physics capabilities at the future muon collider facility. In addition to {mu}{sup +}{mu}{sup -} collider itself, the facility provides other possibilities. Among the possibilities, we present muon-proton collider and neutrino fixed target programs at the muon collider facility. This {mu}-p collider program extends kinematic reach and luminosity by an order of magnitude, increasing the possibility of search for new exotic particles. Perhaps most intriguing DIS prospects come from utilizing high intensity neutrino beam resulting from continuous decays of muons in various sections of the muon collider facility. One of the most interesting findings is a precision measurement of electroweak mixing angle, sin{sup 2}{theta}{sub W}, which can be achieved to the precision equivalent to {delta}M{sub W}{approximately} 30MeV

Yu, J., FERMI

UNT (University of North Texas) Digital Library

F Fermi National Accelerator LaboratoryFERMILAB-Conf-98/201-EDIS Prospects at the Future Muon Collider FacilityJaehoon YuFor the Muon Collider Collaboration andDIS Working Group at the FMC WorkshopFermi National Accelerator LaboratoryP.O. Box 500, Batavia, Illinois 60510July 1998Published Proceedings of the 6th International Workshop on Deep Inelastic Scattering and QCD (DIS98), Brussels, Belgium, April 4-8, 1998Operated by Universities Research Association Inc. under Contract No. DE-AC02-76CH03000 with the United States Department of EnergyDisclaimerThis report was prepared as an account of work sponsored by an agency of the United StatesGovernment. Neither the United States Government nor any agency thereof, nor any oftheir employees, makes any warranty, expressed or implied, or assumes any legal liability orresponsibility for the accuracy, completeness, or usefulness of any information, apparatus,product, or process disclosed, or represents that its use would not infringe privately ownedrights. Reference herein to any specic commercial product, process, or service by tradename, trademark, manufacturer, or otherwise, does not necessarily constitute or imply itsendorsement, recommendation, or favoring by the United States Government or any agencythereof. The views and opinions of authors expressed herein do not necessarily state or reectthose of the United States Government or any agency thereof.DistributionApproved for public release; further dissemination unlimited.DIS PROSPECTS AT THE FUTURE MUON COLLIDERFACILITYJAEHOON YU(for the Muon Collider Collaboration & DIS working group at the FMC workshop)MS309, FNAL, P.O. Box 500, Batavia,IL 60510, USAE-mail: yu@fnal.govWe discuss prospects of deep inelastic scattering physics capabilities at the futuremuon collider facility. In addition to +  collider itself, the facility providesother possibilities. Among the possibilities, we present muon-proton collider andneutrino xed target programs at the muon collider facility. This    p colliderprogram extends kinematic reach and luminosity by an order of magnitude, in-creasing the possibility of search for new exotic particles. Perhaps most intriguingDIS prospects come from utilizing high intensity neutrino beam resulting from con-tinuous decays of muons in various sections of the muon collider facility. One of themost interesting ndings is a precision measurement of electroweak mixing angle,sin2W , which can be achieved to the precision equivalent to MW  30MeV.1 IntroductionLepton colliders have been used, in general, for precision measurements. HighEnergy physics eld has been performing precision measurements using electron-position (e e+) colliders due to the fact that electrons do not decay in theacceleration process. However, e e+ colliders have diculties in increasingcenter of mass energy,ps, due to synchrotron radiation energy losses of elec-trons (positrons) which is proportional to 1m4e. Thus in order to increase thecenter of mass energy of an e e+ collider one needs a larger physical size of thecollider ring. Since muons, on the other hand, have mass of 200 times biggerthan electrons, the synchrotron radiation in a +  collider is 10 10 less thanan e e+ collider, enabling higherps with the same ring size.Less radiation energy loss reduces beam momentum spreads and allowsprecision measurements of any possible resonance states at the givenps. Inaddition, since the Higgs coupling is a Yukawa coupling that is proportionalto the square of the mass of the initial state particles 1, the Higgs productioncross section at the muon collider is a factor 104 bigger than that from e+e colliders at the sameps, above the Higgs mass threshold.The baseline strategy for the muon collider complex is as follows : 1) Startout with intense 16GeV proton sources with the beam intensity of 6  1020protons/year eventually increasing to 1:5 1022 protons/year 2. 2) These highintensity protons produce extremely intense low energy muons and provide1Figure 1: A schematic view of a muon collider facility.8 1019 muons/year, reaching up to 2 1021 muons/year.Figure 1 shows a schematic view of a muon collider facility. The discus-sions presented in this paper consider the following two options : 1)    pcollider program with 200GeV muon beam from the muon collider on 1TeVprotons from Tevatron. 2) neutrino xed target program using extremely in-tense neutrino beam resulting from the decays of 250GeV muons.2 Muon-Proton (  p) Collider OptionCharged lepton-proton colliders have been used for classical deep inelastic scat-tering experiments, providing ideal means of probing nucleon structure. Thusone of the options in the +  collider complex is the  p collider program us-ing 200GeV  extracted from the muon collider on 1000GeV protons from theTevatron. Table 1 compares this   p collider machine parameters 3 to those2Table 1: Comparison of p collider machine parameters to HERA.FMC HERAEl 200GeV  27.5 GeV e (e+)Ep 1000GeV 800GeVQ2  8 105GeV2  9 104GeV2R Ldt 10fb 1=yr 1fb 1=lifetimeof HERA's, including the HERA II. As can be seen in the table, signicantimprovements can be obtained in kinematic reach and integrated luminosity,increasing both by a factor of 10.3 DIS in   p ColliderMost signicant improvement one would expect in   p collider option comesfrom increased kinematic reach and the integrated luminosity. Figure 2 showsthe kinematic reach in log10(Q2) vs log10(x) plane, demonstrating the increasedQ2 and x reach by about a factor of 10 relative to HERA. This extendedkinematic reach in x would enable probing gluon saturation regions, indicatedas a shaded area in the gure, in x < 10 5 where the BFKL dynamics wouldplay a role. However, reaching to this very low-x would require a detectorcoverage down to a very small angle ( = 179o). This extreme small angleFigure 2: The kinematic reach for an asymmetric    p machine. No  collider specicbackgrounds have been considered. The nominal y and  cuts which correspond to HERAhave been applied.3Figure 3: Energy spectra of neutrino beam from 10m straight section of 250GeV ring (left)and RLA3 (right).coverage is the biggest hurdle in the p collider due to the electron backgroundfrom the constant decay of muons in the ring and the nite physical size of thebeam pipe.The extended reach in Q2, due to higherps and a factor of 10 increase inluminosity, would result in higher statistics up to Q2 = 105 regions, allowingimproved sensitivity in exotic particle searches. The conguration given inTable 1 results in 1 million events per year with Q2 > 5000GeV2, comparedto 326 events from ZEUS experiment4 in this region withR Ldt = 34pb 1. Thishigh Q2 reach also increases the sensitivity for scalar lepto-quark to MLQ =800GeV to 3 10 2, assuming ps = 1TeV and R Ldt = 10fb 1.4 Neutrino Beam From Muon CollidersPerhaps, most intriguing byproduct of the muon collider is very intense neu-trino beam ( and e) from the continuous decays of muons in the straightsections of the muon collider facility 5. One can expect the neutrino beam ina small straight sections in two components of the muon collider complex thatcan be seen in Fig. 1. The two are recirculating linac (RLA3) and the storagering.Figure 3 shows the neutrino energy spectra from these two sections of themuon collider 6, assuming 10m straight sections. Since the angular dispersion4D2DipoleDipoleTPC&CerenkovEMHadronicµν  ν eµToroidNeutrino DetectorDrift ChambersCalCalorimeterFigure 4: A light target experiment with a generic neutrino detector. The target in thisgure is a 1m thick D2 with a few layers of silicon vertex detector sandwiched inside.of the neutrinos is inversely proportional to the Lorentz  factor of muons,the neutrino beam resulting from the two straight sections with E = 250GeVare very well collimated. Expected neutrino uxes from these two sections areapproximately 1000 time that of currently most intense neutrino beam seen atthe NuTeV experiment. Due to the high neutrino ux many DIS possibilitieslie in the facility.4.1 Current Neutrino ExperimentsIn order to compare the muon collider neutrino program prospects with thecurrent experiments, it is benecial to review current neutrino experiments.The most common characteristics of the current neutrino experiments is theuse of heavy target detectors in order to increase statistics, given relatively lowneutrino ux. However, using heavy target introduces undesirable features tophysical measurements such as: 1) nuclear eects up to  30% with respect tobare proton target, 2) target dependent isovector corrections, 3) coarse graincalorimetric detectors introduces poor analysis resolution, and 4) ne graindetectors, in general, have poor energy resolution. Despite the fact that theneutrino experiments have the above disadvantages, the neutrino DIS is theonly source of measuring q   q and Vdc, and provides precision measurementof sin2W .54.2 A Neutrino Experiment at the Muon Collider FacilityUnlike the current massive target neutrino experiments, one can imagine anexperiment with a light target (H2 or D2) followed by a generic detector thatcan distinguish electrons from muons resulting from charged-current (CC) in-teractions of  or e. Since the neutrino ux expected from the muon collideris 1000 times higher than current beam, one can obtain sucient statisticseven with light neutrino targets. Figure 4 shows a schematic view of such anexperiment.5 DIS Physics at the Neutrino BeamDue to the intensity of the neutrino beam from the decays of muons in thestraight sections of the muon collider, one would expect large improvements inthe current neutrino physics programs. The rst and most immediate measure-ment one can think of is a precision measurement of nucleon structure functionxF3 which is the only source of q q and is currently statistics limited. Precisemeasurement of xF3 would provide accurate information on valence quarks aswell as strange and charm sea quarks.Heavy quark production measurement is currently statistics limited. Onlydi-muon nal state is used for heavy quark production in present measure-ments, due to immediate showering of electrons resulting from decays of charmedmesons. On the other hand, the experiment shown in Fig. 4 would allow mea-surements using more, if not all, di-lepton (, ee, and e) nal states resultingin a total of  400; 000 di-lepton events per year compared to current level of 5000 events per entire experiment. This large increase in statistics wouldallow accurate measurements of CKM matrix elements, j Vcs j2 and j Vdc j2.Using a silicon target that is equivalent to  3m H2 would result in about20 events/year of (e) + b(b) nal state assuming 10m straight section of thecollider. One would be able to increase statistics by lengthening the straightsection from 10m to 100m, using thicker target, or running longer. This in-creased statistics would allow precision measurement of j Vub j2. One can alsomeasure neutrino and proton spins, using expected 1million events on 200kgtarget resulting in a 2% measurement of s.6 Measurement of sin2WMeasurements of sin2W at the heavy target experiments suer from largestatistical uncertainty as well as experimental systematic uncertainties in dis-tinguishing CC from neutral current (NC) interactions 7. Since the targetdetectors are heavy materials, the existence of e in the beam causes the cur-6rent algorithms of distinguishing CC from NC using an event length variablesto fail, because the CC interaction from e looks identical as the NC eventsfrom  due to immediate showering of electrons. However, using the exper-iment shown in Fig. 4, in principle, completely eliminates the experimentaluncertainties resulting from the denitions of CC and NC events.In addition, since the beam is always a mixture of e and , CC inter-actions from both types of neutrinos can be used for sin2W measurement,resulting in 20million neutrino events in a year from 1m thick H2 target. Apreliminary result from NuTeV experiment suers from statistical uncertaintyof the order 1% based on  1:5 million neutrino events and major experi-mental systematic uncertainties from the use of length variable of the order0.2% 8. Comparatively, one can expect a dramatic reduction in experimentalsystematic and statistical uncertainties in neutrino experiments in the muoncollider facility, resulting in a measurement equivalent to MW = 30 MeV9which is comparable to that expected from the TeV33 in the year 2010, usinga traditional MT t.7 Technical ChallengesThe most important challenge in the muon collider is a fast and eective cool-ing of the low energy muon beam produced from 8GeV proton interactionson a production target, because the mean life time of muons is 2.2sec. E-ciency of capturing as many muons as possible and of transporting them intoacceleration is the most crucial factor in determining the success of a muoncollider. Currently many ideas, including an ionization cooling, have been sug-gested and the muon collider collaboration has recently proposed an ionizationcooling experiment 10 at Fermilab.In addition, there are other challenges to overcome, such as : ecient fo-cusing, eective shielding of background from  decays, possible health hazardsdue to extreme intensity of neutrinos, extensive and eective beam monitoring,etc.8 ConclusionsDespite many technical challenges listed in the previous section, the muoncollider facility provides exciting possibilities in DIS physics. The  p collideroption would open up a maximal reach in Q2, extending the searches of exoticparticles. Reaching to very low x (x  10 5) to probe gluon saturation regionand to study BFKL dynamics is limited due to electron background in the beamresulting from muon decays as well as an angle limitations of the detectors.While this 200GeV  on 1000GeV proton is the option from the rst muon7collider, in a longer term future, it is feasible to build a  p collider with 2 TeV on 1 TeV protons with a next generation +  collider withps = 4TeV.What is most interesting byproduct of the muon collider is xed targetprograms using well understood high ux neutrino beam. A factor of 1000increase in neutrino ux relative to present neutrino experiments provides widerange of DIS physics possibilities in addition to the +  collider itself.In conclusion, the muon collider is the facility for High-Energy communityto open up rich physics capabilities in 10 to 15 years down the road. In orderto realize this exciting facility, it is important to have constant interest andsupport within the High-Energy community for the program.References1. A. Abbasabaddi, D. Bowser-Chao, D.A. Dicus, and W.W. Repko,UICHEP-TH-97-17, to be published in the proceedings of the Workshopon Physics at the First Muon Collider, Fermilab, Batavia, IL, USA, Nov.19972. C. Ankenbarndt and S. Geer., \Acelerator Scenario and Parameters forthe First Muon Collider and Front-end of a Muon Collider,"FERMILAB-Conf-98/086, March (1998)3. V.D. Shiltsev, FERMILAB-Conf-97/114 (1997)4. G. Howell and D.Williams, in these proceedings.5. S. Geer, Phys. Rev. D57, 1 (1998)6. D.A.Harris & K.S.McFarland, MIT-LNS-98-276, to be published in theproceedings of the Workshop on Physics at the First Muon Collider,Fermilab, Batavia, IL, USA, Nov. 19977. K.S.McFarland et al., CCFR/NuTeV Collaboration, Eur. Phys. J. C1,509 (1998)8. J.Yu, NuTeV collaboration, in these proceedings.9. J.Yu & A.Kotwal, Fermilab-Conf-98/027, to be published in the proceed-ings of the Workshop on Physics at the First Muon Collider, Fermilab,Batavia, IL, USA, Nov. 199710. S. Geer, Muon Collider Collaboration, \Ionization Cooling Research andDevelopment Program for a High Luminosity Muon Collider," Fermilab-Conf-98/136, presented at the Workshop on Physics at the JHF (JHF98),KEK, Tsukuba, Ibaraki, Japan, March 4-7 (1998) ; Refer to the Web site,http://www.fnal.gov/projects/muon collider/cool/cool.htmlfor cooling experiment proposal8

DIS prospects at the future muon collider facility

http://citeseerx.ist.psu.edu/viewdoc/summary?doi=10.1.1.341.1093

DIS Prospects at the Future Muon Collider Facility

Abstract

Similar works

Full text

Available Versions

UNT (University of North Texas) Digital Library