accelerator neutrino beams as used in cross section experiments
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Accelerator Neutrino Beams as used in cross section experiments. Sacha E. Kopp University of Texas at Austin. The Big Picture. Many come to this business from osc. expt Previous dedicated cross section experiment was in 1980’s. Let us agree that - PowerPoint PPT PresentationTRANSCRIPT
Accelerator Neutrino Beamsas used in
cross sectionexperiments
Sacha E. Kopp
University of Texas
at Austin
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 (E) ± (E)?
A Little Historical Foundation
G.T. Danby et al, Physical Review Letters 9 36 (1962)
Modern Beam
• Same physics principle
• But add focusing
• And add instrumentation
TargetHorns
Decay PipeAbsorber
Muon Monitors
Rock
μ+
π+
10 m 30 m675 m
5 m 12 m 18 m
figure courtesy Ž. Pavlović
Hadron Monitor
νμ
Many Neutrino Beams!
S. Kopp, “Accelerator Neutrino Beams,” Phys. Rep. 439, 101 (2007)
Many old Horror Stories
• 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
NAL Team & Neutrino Horn Cone, 1974several dramatic horn failures
CERN PS beamasymmetry in horn field
J.C. Dusseux et al, CERN-72-11, 1972CERN WANF misalignment
L. Cassagrande, CERN-96-06
adventure
Ah, so things are better today!
• primary beam intensity ±2%, position ±90m• horn geometry (shape) < 0.5mm• horn alignment ±0.5mm• horn field to ±0.5%
Why focus anyway?
• Feynman scaling in xF ~ pL/p0
• No scaling for
• ‘Cocconi divergence’
proton
p0
pTpz
p + A → + X
Why focus anyway?
• ‘Cocconi divergence’
• Neutrino divergence
• Reduce divergence ~3, flux goes up by ~ 25
L. Ahrens et al, Phys. Rev. D 34, 75 - 84 (1986)
Horns ‘O Plenty
• On axis
beam energy tune is selected by
NuMI Low Energy Beam
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
NuMI Variable Energy Beam
targetHorn 1
Horn 2
Pions with pT=300 MeV/c and
p=5 GeV/cp=10 GeV/cp=20 GeV/c
Slide the target in/out of the 1st horn
M. Kostin et al, “Proposal for Continuously-Variable Neutrino Beam Energy,” Fermilab-TM-2353-AD (2001).
10 cm
100 cm
250 cm
The Call of the Mermaid
“I’ll just let [Harp/NA69/NA49/MIPP/SPY] solve my
problems”-- Hans Christian Anderson
Does any one recall the fate of the person that answers the mermaid’s call?
Atherton400 GeV/c p-Be
Barton100 GeV/c p-C
SPY450 GeV/c p-Be
You Really Wanted (E)(xF,pT)
NuMI HE BeamNuMI HE Beam
NuMI LE BeamNuMI LE Beam
p (GeV/c)
p T (
GeV
/c)
Modern Data Sets are $%#&! Good!
• Modern data sets better than original ‘beam surveys’– single particle detection– particle ID– large acceptance
• So can’t we just use this to map (xF,pT)??
pT (GeV/c)
d/d
p T (
mb/
GeV
/c)
eg: C. Alt et al, Eur.Phys.J.C49:897-917,2007
No! (1) Thick Target Effects
• Most ptcle production exp’ts on thin targets
• Nu production target ~ 2int
• Reinteractions!
• 20-30% effect
Min
iBoo
NE
NuMI
CNGS
J-PARC
figure courtesy Z. Pavlovic
No! (2) In-beam variations
18/25
• 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 (Mons)
• Thermal variations in your beam MC?
NuMI-only
figure courtesy L. Loiacono
NuMI-Collider Combined mode
No! (3) Beam Degradations?
Each data point is one
month’s data
Neutrino Energy (GeV)
Eve
nts
/ 10
16P
OT
/ G
eV • 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
figure courtesy M. Dorman
No! (4) Downstream Interactions
Near Decay Pipe
• Wrong sign neutrinos have huge contribution
• What if you run a nubar beam?! X3 worse effect!
• Not covered by particle production experiments!figure courtesy A. Himmel
CNGS: Earth B Field?!
NeutrinoFocus +
Anti-neutrino
Focus
They See shift of 6.4 cm (consistent with 0.3 Gauss)
figure courtesy E. Geschwendtner
A Cautionary Tale
• CERN PS team did particle prod @ IHEPJ.V. Allaby, et al., Phys. Lett. 29B 48 (1969)
• In-situ flux using Mons 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.
The light at the end of the
Tunnel!
• Just need an in situ measure of (xF,pT)
• No extrapolation to ‘real experiment’
• Averages over effects in beam
In situ Muon Monitor Flux• CERN
PS• CERN
WANF• IHEP• FNAL
E616• Typical
~20%
• also FNAL NuMI (L. Loiacono, this workshop)
In situ Flux Using Neutrinos
A. Aguilar et al., arXiv:0806.1449
MiniBooNE
• Compare HARP flux to QEL events.
• Scale flux by 1.21!• What about K2K?!
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
26
NuMI Flux Tuning
• Fit all 7 beam runs.
• Fit νμ and νμ
spectra• But uses
inclusive events!
• To be replicated by MINERvA using QELs• MINOS: also low- events (see M. Kordosky’s talk)
Phys. Rev. D77, 072002 (2008).
NuMI Mon Flux
• Similar to tuning by MINOS, but uses Mon event rates (no error from x-sec)
• L. Loiacono, poster at this workshop
• 20-30% errors
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?
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)
Grandfather of All “Beams”*
* 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)
p p,K,
31/25
FNAL NBB
NB: Apparently Mon not used because of backgrounds
Fluxes came from these
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.
D. Bloess, et al., Determination of the spectrum in the CERN 1967 neutrino
experiment, Nucl. Inst. Meth. 91 (1971) 605.
35/25
Comparison to Alcove 1 DataGNuMI Monte Carlo Muon Monitor Data
36/25
Simultaneous fit to Antineutrinos• Antineutrinos come from off the target• Our simultaneous and anti- fit came surprisingly close to
new p+C data available from CERN NA49 experiment!