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Accelerator Neutrino Beams as used in cross section experiments

This article discusses the history, challenges, and advancements in accelerator neutrino beams, their cross-section experiments, and the importance of focusing and instrumentation. It also highlights the improvements in beam quality and data sets, as well as the need for in-situ measurements and flux tuning.

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Accelerator Neutrino Beams as used in cross section experiments

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  1. Accelerator Neutrino Beamsas used incross sectionexperiments Sacha E. Kopp University of Texas at Austin

  2. The Big Picture • Many come to this business from osc. expt • Previous dedicated cross section experiment was in 1980’s. • Let us agree that • Oscillation experiments optimized differently. What is f(En) ± df(En)?

  3. A Little Historical Foundation G.T. Danby et al, Physical Review Letters 9 36 (1962)

  4. Modern n Beam Muon Monitors νμ Absorber μ+ Decay Pipe Horns Target π+ 18 m 5 m Rock 30 m 12 m Hadron Monitor 10 m 675 m figure courtesy Ž. Pavlović Same physics principle But add focusing And add instrumentation

  5. Many Neutrino Beams! S. Kopp, “Accelerator Neutrino Beams,” Phys. Rep. 439, 101 (2007)

  6. adventure Many old Horror Stories NAL Team & Neutrino Horn Cone, 1974 several dramatic horn failures CERN PS beam asymmetry in horn field J.C. Dusseux et al, CERN-72-11, 1972 CERN WANF misalignment L. Cassagrande, CERN-96-06 • And several dramatic failures of targets • H. White, Fermilab-TM-662, 1976 • A. Mann, Neutrino Interactions With Electrons and Protons: An Account of an Experimental Program in Particle Physics in the 1980s, AIP Press

  7. Ah, so things are better today! primary beam intensity ±2%, position ±90mm horn geometry (shape) < 0.5mm horn alignment ±0.5mm horn field to ±0.5%

  8. Why focus anyway? p + A→p+ + X p proton pT p0 pz q Feynman scaling in xF ~ pL/p0 No scaling for ‘Cocconi divergence’

  9. Why focus anyway? q n p m ‘Cocconi divergence’ Neutrino divergence Reduce divergence ~3, flux goes up by ~ 25 L. Ahrens et al, Phys. Rev. D 34, 75 - 84 (1986)

  10. Horns ‘O Plenty On axis n beam energy tune is selected by

  11. NuMI Low Energy Beam

  12. Era of Precision-Focused Beams Mechanical tolerances on horns improved Near-analytic calculations or error conditions Errors large at ‘edge’ of focusing Z. Pavlovic, “A Measurement of Muon Neutrino Disappearance in the NuMI Beam,” PhD Thesis, UT Austin 2008

  13. NuMI Variable Energy Beam Slide the target in/out of the 1st horn 10 cm 100 cm 250 cm Pions with pT=300 MeV/c and p=5 GeV/c p=10 GeV/c p=20 GeV/c target Horn 1 Horn 2 M. Kostin et al, “Proposal for Continuously-Variable Neutrino Beam Energy,” Fermilab-TM-2353-AD (2001).

  14. The Call of the Mermaid Does any one recall the fate of the person that answers the mermaid’s call? “I’ll just let [Harp/NA69/NA49/MIPP/SPY] solve my problems” -- Hans Christian Anderson

  15. You Really Wanted fn(En)fn(xF,pT) NuMI LE Beam Atherton 400 GeV/c p-Be Barton 100 GeV/c p-C SPY 450 GeV/c p-Be pT (GeV/c) NuMI HE Beam p (GeV/c)

  16. Modern Data Sets are $%#&! Good! ds/dpT (mb/GeV/c) eg: C. Alt et al, Eur.Phys.J.C49:897-917,2007 • Modern data sets better than original ‘beam surveys’ • single particle detection • particle ID • large acceptance • So can’t we just use this to map fn(xF,pT)?? pT (GeV/c)

  17. No! (1) Thick Target Effects MiniBooNE J-PARC CNGS NuMI figure courtesy Z. Pavlovic Most ptcle production exp’ts on thin targets Nu production target ~ 2lint Reinteractions! 20-30% effect

  18. No! (2) In-beam variations • Temperature in NuMI target hall varies by 8°C as beam power cycles. • Causes change in horn current ~1 kA • Observe direct variation in beam flux (mMons) • Thermal variations in your beam MC? NuMI-only NuMI-Collider Combined mode figure courtesy L. Loiacono

  19. No! (3) Beam Degradations? Each data point is one month’s data • Started after installation of new target. • Have ruled out horns (swapped) • Have ruled out He leak in decay volume • Consistent with density variation at shower max Events / 1016POT / GeV figure courtesy M. Dorman Neutrino Energy (GeV)

  20. No! (4) Downstream Interactions • Wrong sign neutrinos have huge contribution • What if you run a nubar beam?! X3 worse effect! • Not covered by particle production experiments! Near Decay Pipe figure courtesy A. Himmel

  21. CNGS: Earth B Field?! Neutrino Focus p+ Anti-neutrino Focus p- They See shift of 6.4 cm (consistent with 0.3 Gauss) figure courtesy E. Geschwendtner

  22. A Cautionary Tale • CERN PS team did particle prod @ IHEP J.V. Allaby, et al., Phys. Lett. 29B 48 (1969) • In-situ flux using mMons suggested X2 off?! D. Bloess, et al, CERN-69-28 (1969), Nucl. Inst. Meth. 91 (1971) 605. • Particle production round two – ok to 15% J.V. Allaby, et al., CERN-70-12.

  23. The light at the end of the Tunnel! • Just need an in situ measure of fn(xF,pT) • No extrapolation to ‘real experiment’ • Averages over effects in beam

  24. In situ Muon Monitor Flux • CERN PS • CERN WANF • IHEP • FNAL E616 • Typical ~20% • also FNAL NuMI (L. Loiacono, this workshop)

  25. In situ Flux Using Neutrinos A. Aguilar et al., arXiv:0806.1449 MiniBooNE P. Astier et al., Nucl. Instr. Meth. A 515 (2003) 800. NOMAD • L. Ahrens et al, Phys. Rev. D 34, 75 - 84 (1986) • K. McFarland, et al., arXiv:hep-ex/9806013 Compare HARP flux to QEL events. Scale flux by 1.21! What about K2K?!

  26. NuMI Flux Tuning Phys. Rev. D77, 072002 (2008). • Fit all 7 beam runs. • Fit νμ and νμspectra • But uses inclusive events! • To be replicated by MINERvA using QELs • MINOS: also low-n events (see M. Kordosky’s talk)

  27. NuMI mMon Flux Similar to tuning by MINOS, but uses mMon event rates (no error from n x-sec) L. Loiacono, poster at this workshop 20-30% errors

  28. Summary • Flux needs for oscillation experience far less stringent than for cross section exp’t. • Ab initio measurements don’t replicate in situ effects – especially in intense beams! • How can we design for cross section measurements and checks UP FRONT?! • In situ measurements must be independent of the cross sections to be measured – use QELs or elastic scatters?

  29. References • Proc. of Int. Workshop on Neutrino Beams and Instrumentation (NBI) • http://proj-cngs.web.cern.ch/proj-cngs/NBI2006/NBI2006.html • http://www.hep.utexas.edu/nbi2005/ • http://www-ps.kek.jp/nbi2003/ • http://proj-cngs.web.cern.ch/proj-cngs/2002_workshop/announce_1.html • Proc. Informal Workshops on Neutrino Beams • CERN-63-37, CERN-65-32, CERN-69-28 • S. Kopp, “Accelerator Neutrino Beams,” Phys. Rep. 439, 101 (2007)

  30. Grandfather of All n “Beams”* nm p,K,p p m,nm * G.T. Danby et al, Observation of high-energy neutrino reactions and the exisitence of two kinds of neutrinos,” Phys. Rev. Lett. 9 36 (1962)

  31. FNAL NBB NB: Apparently mMon not used because of backgrounds Fluxes came from these

  32. A Cautionary Tale (2) • ANL did particle production experiment on “actual” target: R.A. Lundy, et al., Phys. Rev. Lett. 14 (1965) 504. • Motivated by bad fit to Sanford-Wang, did second round with limited points J.G. Asbury, et al., Phys. Rev. 178 (1969) 2086. G.J. Marmer, et al.,Phys. Rev. 179 (1969) 1294. • Finally had to do “round three” Y. Cho, et al., Phys. Rev. D 4 (1971) 1967.

  33. D. Bloess, et al., Determination of the n spectrum in the CERN 1967 neutrino experiment, Nucl. Inst. Meth. 91 (1971) 605.

  34. Comparison to Alcove 1 Data GNuMI Monte Carlo Muon Monitor Data

  35. Simultaneous fit to Antineutrinos • Antineutrinos come from p- off the target • Our simultaneous nm and anti-nm fit came surprisingly close to new p+C data available from CERN NA49 experiment! n

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