Variation in MC prediction of MB nu flux

Hadron Production Results from the HARP Experiment Linda Coney For the HARP Collaboration Beach 2008 June 27, 2008

Outline Introduction Experiment & Detector Data Hadron Production Results Results for Accelerator Based Conventional Neutrino Beams Results for Extended Air Showers and Atmospheric Neutrinos Results for Neutrino Factory designs Results as Input for Hadron Production Models Conclusions

Why Hadron Production Measurements? Neutrino physics moving from discovery to precision measurement For conventional beams Hadron production uncertainties have big impact on neutrino flux predictions: overall flux, energy spectrum, flavor composition, etc. Weak decays of µ, π and K mesons produce a well understood spectrum of neutrinos. The flux uncertainty comes from the production cross section of the parent particle and its subsequent scattering in target materials. Phenomenological parameterizations can be valid over limited energy and angle ranges, more useful at higher energies (> ~15 GeV) (e.g. Sanford- Wang or others) For neutrino factory Want well understood high intensity neutrino beam Need optimize parent pion production at front end of machine

Why Hadron Production Measurements? Extended air showers and atmospheric neutrinos Challenges exist for accurate atmospheric neutrino flux predictions Primary cosmic ray spectrum Hadronic interactions determine shower development, particularly interaction of primary with nuclei Incoming protons, π+, π- Variation in MC prediction of MB nu flux Hadron Production Data as input for MC Generators There are large discrepancies in the various hadron production models used in MC generators (MARS, FLUKA,

Experimental Meson Production Data Earlier data exists but a match between energy, angular range, and nuclear target is required to avoid systematic errors due to interpolation or extrapolation in (E beam,θ,a),a) At energies above ~15 GeV and in certain angular ranges, situation is more reliable for extrapolating to nearby energies Most historical data is in the form of single-arm spectrometer measurements

HARP (Hadron Production Experiment) at CERN Harp is a large angle spectrometer designed to measure hadron production from various targets and a range of incident beam momenta Neutrino factory studies Atmospheric neutrino predictions Neutrino flux predictions for recent accelerator based neutrino beam experiments K2K MiniBooNE Input for hadron generators (GEANT4)

HARP at CERN 24 institutes ~120 collaborators Detector on T9 beam line at CERN PS HARP: barrel spectrometer (TPC) + forward spectrometer (NOMAD DCs) to cover the full solid angle, complemented by particle-id detectors

HARP Beam and Target Settings Beam Settings: 2-15 GeV/c momenta Both positively and negatively charged beams Pure p, pi+,pi- beams Target Settings: From H to Pb (A=1-207) 2% - 200% λ I thickness 400 Million events Only 5% interaction length target discussed here ** H Be Ta Cu C N O Al Sn Pb

HARP: Large Angle and Forward Spectrometers Beam BCA TOF A BCB TOF B BS MWPC RPC TDS Solenoid magnet TPC NDC NDC NDC ECAL HALO A beam HALO B FTP target Dipole Magnet Large angle spectrometer CKOV TOF TPC: ArCO2 Solenoid: 0.7T Field Beam Detectors The HARP detector at the CERN PS NIM A 571 (2007) 527 561 Forward spectrometer 350 < θ < 2150 mrad 0.1 < p (GeV/c) < 0.8 30 θ 210 mrad 0.75 < p (GeV/c) < 8

HARP Detector: Target & TPC target MWPCs Beam HALO Veto entries 140 120 100 π+ 80 60 p RPC modules 40 20 0 200 400 600 800 1000 1200 1400 1600 de/dx (ADC counts)

Track Reconstruction Forward Spectrometer Large Angle Spectrometer Unit-area normalized momentum distributions of beam pions for different beam settings: momentum scale understood to 2% 4% momentum resolution at p=3 GeV/c Missing mass squared in pp elastic data: m X2 = (p beam +p target -p TPC ) p beam : incident protons from 3 GeV/c beam and beam instrumentation measurements p target : target protons at rest in H target p TPC : 4momentum as measured by TPC

Forward Spectrometer: Overlapping PID Detectors P (GeV) π/p π/k π/e 0 1 2 3 4 5 6 7 8 9 10 TOF CERENKOV TOF CERENKOV CERENKOV CALORIMETER CAL TOF CERENKOV Particle ID variables reconstructed momentum β from Tof system Npe from Cerenkov Energy deposited in Calorimeter Particle identification algorithms for the HARP forward Spectrometer, NIM A 572 (2007) 899

Results for Accelerator Based Neutrino Beams Hadron production uncertainties have big impact on neutrino flux predictions: overall flux, energy spectrum, flavor composition, etc. Flux uncertainty comes from the production cross section of the parent particle.

HARP Measurement for K2K K2K: Disappearance experiment to confirm atmospheric oscillation Beam particle: proton Beam momentum: 12.9 GeV/c Target: 5% λ Al Produced particle: π+

HARP 12.9 GeV/c p-al Results Beam particle: proton Beam momentum: 12.9 GeV/c Target: 5% λ Al Produced particle: π+ 30< θ <210 mrad 0.75< p <6.5 GeV/c HARP p-al data 12.9 GeV/c: M. G. Catanesi et al., HARP, Nucl. Phys. B732 (2006) 1 K2K results, with discussion of production measurement: M. H. Ahn et al., K2K, Phys. Rev. D74 (2006) 072003. [arxiv:hep-ex/0606032] HARP results in black, Sanford- Wang parameterization of HARP results in red Parameterization used to: incorporate HARP data in K2K and MiniBooNE beam MC Translate HARP pion production uncertainties into flux uncertainties Compare HARP results with previous results F/N contribution to uncertainty in number of unoscillated muon neutrinos expected at Super-K reduced from 5.1% to 2.9% with HARP p-al @ 3, 5, 8, 12 GeV/c available.

Decay region 25 m 50 m 450 m Primary beam Secondary beam Neutrino beam ν µ π + + + HARP Measurement for MiniBooNE Short lived pions and kaons decay to produce a forward beam of mixed neutrinos aimed at the MiniBooNE detector Need to understand neutrino flux e 0 0 0 0 µ µ µ µ µ ν µ π ν π ν π ν µ π ν µ ν ν ν µ π + + + + + + + + + + + + ± ± + + + + + + + + + m m K e K e K K K e e e

HARP 8.9 GeV/c p-be Results Beam particle: proton Beam momentum: 8.9 GeV/c Target: 5% λ Be Produced particle: π+ HARP (data points), Sanford-Wang parameterization (histogram) 0.75 < p < 6.5 GeV/c 30 < θ < 210 mrad Relevance for MiniBooNE 80.8% HARP p-be data 8.9 GeV/c: M. G. Catanesi et al., EPJC 52, 29 53 (2007) MiniBooNE, A.A.Aguilar-Arevalo et al., PRL 98, 231801 (2007)

HARP 8.9 GeV/c p-be Results Beam particle: proton Beam momentum: 8.9 GeV/c Target: 5% λ Be Produced particle: π+ 5% measurement over 0.75 < p < 6.5 GeV/c 30 < θ < 210 mrad 10% bin-by-bin measurement Compares well with beam momentum-rescaled BNL E910 at 6, 12 GeV/c Blue histogram is beam MC prediction tuned with HARP and E910 Preliminary proton, π- production results (for anti-ν) HARP p-be data 8.9 GeV/c: M. G. Catanesi et al., EPJC 52, 29 53 (2007) MiniBooNE, A.A.Aguilar-Arevalo et al., PRL 98, 231801 (2007)

Results for Extended Air Showers and Atmospheric Neutrinos Challenges exist for accurate atmospheric neutrino flux prediction Hadronic interactions determine shower development, particularly interaction of primary with nuclei

Results for Extended Air Showers and Atmospheric Neutrinos Primary particle p p+c π + p γ p γ e + π - π 0 Κ e - n π + π 0 γ γ e + e - target π + µ - µ - π + π - Incoming protons and pions - measure: π + and π spectra µ + µ - + Several targets + Forward direction + Relevant energy range: 10-400 GeV p + Cryogenic targets

Results p, π +/- C at 12 GeV/c p-c π+- π + -C π+- π - -C π+- Beam particle: p, π+, π- Beam momentum: 12 GeV/c Target: 5% λ C Produced particle: π+, π- 0.5 < p < 8.0 GeV/c 30 < θ < 240 mrad Filled: piplus Open: piminus Line: SW Stat and syst errors HARP p, π± +C @ 12 GeV/c data including comparison with models: Astropart. Phys. (2008), doi:10.1016/j.astropartphys.2008.02.002

Results p+c, N2, O2 at 12 GeV/c Spectra very similar π + π - Beam particle: p Beam momentum: 12 GeV/c Target: 5% λ C, N2,O2 Produced particle: π+, π- Submitted for publication

Results for Neutrino Factory Need optimize parent pion production at front end of machine Need understand kinematics of pions for detailed neutrino factory design

Results for Neutrino Factory Store 450 GeV muons in a ring with long straight sections Stored beam properties and muon decay kinematics well known small neutrino flux uncertainties Challenge here is not flux uncertainty, but flux optimization: need to optimize collection efficiency of π+ and π produced in the collisions of protons with highz target (eg, Hg) Which proton beam momentum is best, which range acceptable? Accurate knowledge of produced pion kinematics needed for detailed design Measure p distribution with high precision Solid targets high Z

HARP LA Spectrometer Results Beam particle: proton Beam momentum: 3, 5, 8 (8.9), 12 (12.9) GeV/c Target: 5% λ Be,C,Al, Cu, Sn,Ta,Pb Produced particle: π+, π- All thin target data taken in proton beam is available Includes Tantalum, C, Be, Aluminum, Cu, Sn, Lead π± production measured over 0.1 < p (GeV/c) < 0.8, 350 < θ (mrad) < 2150 Good match with typical neutrino factory acceptance (~70%, design dependent) Look at Ta, Pb, Al NuFact design uses Hg

HARP Results for LA p-ta π + Beam particle: proton Beam momentum: 3, 5, 8, 12 GeV/c Target: 5% λ Ta Produced particle: π+ p forward 350 < θ (mrad) < 1550 backward 1550 < θ (mrad) < 2150

Results for LA p-ta π Beam particle: proton Beam momentum: 3, 5, 8, 12 GeV/c Target: 5% λ Ta Produced particle: π forward 350 < θ (mrad) < 1550 backward 1550 < θ (mrad) < 2150

Results for LA Al, Ta, Pb π+ π- Beam particle: proton Beam momentum: 3, 5, 8, 12 (12.9) GeV/c Target: 5% λ Al,Ta,Pb Produced particle: π+, π- π+ π- Ta, Pb similar results Al much lower cross section π+ π- Note: spectrum much steeper in backward direction Higher beam momentum more pions and higher momentum pions Momentum (GeV/c)

Neutrino Factory Optimization Pion yield normalized to beam proton kinetic energy Restricted phase space shown most representative for NuFact designs Optimum yield in HARP kinematic coverage for 5-8 GeV/c beam momenta Same conclusions for Ta target results Pb Full LA fwd Acceptance 350 <θ(mrad)<1550 0.1< p(gev/c)<0.8 350<θ(mrad)<950 Quantitative optimization possible with detailed spectral information available: ~100 (p,θ) data points for 4 beam momentum settings (3-12 GeV/c) each p (GeV/c) 0.25<p(GeV/c)< 0.50 Filled: π+ Empty: π-

Results for Hadronic Generators Previously: little experimental data large uncertainties HARP: provides many target materials and momenta, full PID large solid angle Input/calibration for hadronic generators and models (in collaboration with GEANT4)

Comparison of yields for Solid Targets π + and π integrated yields for p-a for Be, C, Al, Cu, Sn, Ta, Pb C, Be shape clearly differs from Ta,Pb however mid-range targets show smooth transition lighter target saturates out at higher momentum Large Angle forward production only 350 < θ < 950 mrad π π +

π-/π+ Ratios for Heavy and Light Nuclei comparison of p-c π /π + and p-ta π /π + ratios Large Angle forward production only 350 < θ < 1550 mrad p-ta p-c

A-dependence A-dependence of π + and π integrated yields for p-a for Be, C, Cu, Sn, Ta and Pb (3, 5, 8, 12 GeV/c) Large Angle forward production only 350 < θ < 1550 mrad π + π A A

Comparison of LA Results to Previous Data Be π + Be π Cu π + π Al Cu π + π π + π

Comparison of Data with Models Many comparisons with models from GEANT4 and MARS are being done Some examples will be shown for 12 GeV/c Binary cascade Bertini cascade Quark-Gluon string models (QGSP) Frittiof (FTFP) LHEP (successor of GEISHA) MARS Some models do a good job in some regions, but there is no model that describes all aspects of the data.

Models p-al at 12.9 GeV/c HARP vs GEANT4

Models p-be π+ + X at 8.9 GeV/c HARP vs GEANT4

Model comparison: p+c π + +X

Model comparison: p+c π +X

Conclusions HARP has measured pion production by 3 12 GeV/c protons and pions from nuclear targets (from Hydrogen to Lead) in the momentum angular region 0.1 8 GeV/c and 30 2150 mrad Large amount of data published more on the way Results very important MiniBooNE/K2K improved neutrino flux understanding

Particle Production Phase Space Measured π+, π, proton production Regions indicate phase space covered: Forward spectrometer 0.75 < p (GeV/c) < 8 0.030 < θ (rad) < 0.240 Large angle spectrometer 0.1 < p (GeV/c) < 0.8.35 < θ (rad) < 2.15

Track Reconstruction: FWD Spectrometer Track reconstruction with drift chambers and dipole magnet PID with threshold Cherenkov + time-of-flight wall ( +electromagnetic calorimeter) Elastic Scattering Use TPC + FWD One track fwd at beam momentum, one proton LA 3, 5, 8 GeV/c proton on H2 Circles: 30-60 mrad Boxes: 60-100 mrad

Track Reconstruction in TPC Momentum Resolution Momentum Scale 1/p t fractional resolution versus p t from: separate fit of cosmic ray track halves de/dx in 1/ β 2 region (triangles) MC simulation (shaded area) Obtained from de/dx slice in 1/β 2 proton region Consistency within ±2% of all (beam, target) settings with one used in pp elastic analysis

Number of Events

HARP: Beam instrumentation MWPCs Beam composition and direction T9 beam CKOV-A TOF-A CKOV-B TOF-B 21.4 m MWPCs Measure incident beam direction Beam cerenkov Proton selection purity > 98.7% K-π separation at high energy 12.9 GeV Beam Tof k/π /π/p separation at low p Determine T0 K π π k p 3 GeV d Reconstructed vertex (x,y) of beam particles at target Resolution < 1mm Corrected TOF (ps)

Tracking: Track Reconstruction 2 Reused NOMAD drift chambers: 5 modules x 4 (chambers/module) x 3 (planes/module) Top x view Do not use for fit beam z target 1use for fit use for fit TWO WAYS to get momentum: 1 1 2 NDC 1 Do not use for fit dipole magnet 3D track segment DOWNSTREAM, plus successful vertex match» used to measure pion yield. B Downstream track: 99.5% efficiency NDC 2 2 NDC 5 NDC 4 1 NDC 3 2 Vertex4 tracks: 3D track segment DOWNSTREAM, plus 3D segment UPSTREAM» used to measure track reconstruction efficiency of vertex match

Track Reconstruction: Efficiency Measure reconstruction efficiency from data Use redundancy of downstream detectors Use multiple upstream track constraint options Within geometrical acceptance: only focused tracks: + charge θ x < 0 efficiency high and nearly flat in p and theta ε recon 1.2 1 Data MC ε recon 1.2 1 use x 0 Data MC reject 0.8 0.8 0.6 0.6 0.4 0.4 0.2-210 -80 θ y θ x 0 mrad 80 mrad 0.2 0.75 p 6.50 GeV/c -80 80 mrad θ y 0 1 2 3 4 5 6 7 8 p (GeV/c) 0-0.2-0.15-0.1-0.05-0 0.05 0.1 0.15 0.2 θ x (rad)

Track Reconstruction: Momentum Resolution Use Data: Need sample of tracks with known momentum Three methods cover different regions in θ, p Empty target data sets Elastic scattering Time of flight 0.2 0.1 0. theta-p plane : TOF elastics empty target beam 0.51.5 3 5 8 Empty target data sets 1.5, 3.0, 5.0, 8.0, 8.9, 12.0, 12.9, 15.0 GeV/c

Track Reconstruction: Momentum Resolution theta-p plane : 0.2 0.1 TOF elastics Time of Flight 0. Use for lower momentum < 3 GeV/c Open:data, solid:mc empty target beam 0.51.5 3 5 8 Elastic Scattering Make use of TPC, large angle information One track fwd at beam momentum, one proton LA 3, 5, 8 GeV/c proton on H2 Circles: 30-60 mrad Boxes: 60-100 mrad

HARP: Threshold Cerenkov: π/p cerenkov data Filled with C4F10 (perflourobutane) at atmospheric pressure. Pion threshold ~3 GeV/c entries 3 GeV beam particles 1400 1200 1000 800 600 400 200 p π + π inefficiency e + Ckov for 8.9Gev data - beam pions entries 5 GeV beam particles 1200 1000 800 600 400 200 p π inefficiency π + 0 0 5 10 15 20 25 30 35 40 45 50 N phe number of photoelectrons 0 0 5 10 15 20 25 30 35 N phe number of photoelectrons

HARP Time of Flight: π/p beta:p1 {p1<6 && p1>0 && beta<1.05 && beta>0.7 && ftp_mult>0} 1.05 1 0.95 0.9 0.85 0.8 0.75 tof wall 7σ π/p at 3GeV beam ~70 ps 0 1 2 3 3 GeV beam particles 350 250 5 6 12.9 GeV K2K thin target 2500 π+ 300 4 entries planes of scintillator counters discriminate between protons and pions at low momentum Tof wall resolution ~160 ps 0.7 entries target light particles 2000 200 mom < 4.5GeV 1500 150 1000 p 100 50 0-1 -0.5 0 0.5 1 1.5 2 p 500 2 2 m (GeV ) 0-1 -0.5 0 0.5 1 1.5 2 2 2 m (GeV )

HARP: Electron/Hadron Calorimeter CAL Two parallel modules - ECAL, HCAL Vertical scintillator planes e h E 1 E 2 electrons lose most of ECAL HCAL their energy in ECAL E 1 /E ~ 1 & E/p ~ 1. hadrons lose very little energy E 1 /E < 1 & E/p << 1 entries 250 200 150 100 50 0 0 0.2 E/p 0.4 h + 0.6 0.8 1 3 GeV no target e + 1.2 1.4 0.1 0.20.3 0 0.4 0.50.6 1 0.7 0.80.9 E 1 /E

PID performance ions Cherenkov efficiency - pi π/e π/p π/k 1-1 10 0 1 2 3 4 5 6 7 CERENKOV CALORIMETER TOF TOF CERENKOV CERENKOV pions CERENKOV Cherenkov efficiency - prot tons β = d/tc 1.05 1 0.95 0.9 0.85 0.8 0.75 0.1 0.7 0.09 0.65 0.08 0.6 0.07 0.06 0.05 0.04 0.03 0.02 TOF Data - solid points pions protons kaons electrons Monte Carlo - dashed histogram 1 2 3 4 5 6 7 8 p (GeV/c) 2 protons: 1-2% -2 10 0.01 1 2 3 4 5 6 p (GeV/c) 0 1 2 3 4 5 6 7 8 p (GeV/c)

Recipe for Cross-Section Calculation Select events identified as primary protons interacting in the target For each event, reconstruct tracks and their 3-momentum Identify pions among secondary tracks Count protons on target corresponding to selected events Apply corrections, for reconstructed-to-true pion yield conversion: Momentum resolution Spectrometer angular acceptance Track reconstruction efficiency Efficiency and purity of pion identification Other Multiply by physics constants and accurately measured target properties

The Cross Section (p,θ) true absolute normalization Measured Pion Yield Target-out Background Efficiency/migration/correction matrix Primes denote reconstructed quantities i,j are momentum and angle bins α Is the particle type

Cross Section Continued = Primed = measured Unprimed = true

HARP: Cross Section Measurement N π i = ε 1 acc i ε 1 track i M ij ε 1 π j η π j N π j ( p, θ ) true acceptance migration matrix pion purity ( p, θ ) rec tracking efficiency pion efficiency pion yield Raw Particle Yields, Efficiency and Purity determined using data and mc. PID detectors used to develop probability functions for particle types Acceptance, Tracking Efficiency and Matching Efficiency determined using data. Empty target background subtraction done using data. Unfold to express cross section in terms of true quantities done using MC

Correction Factors Correction Type Impact On Cross Section Method Momentum Resolution Shape Data/MC Track Reco Efficiency ~5% up Data Geometric Acceptance ~100-160% up MC/Analytic Pion ID Efficiency: <4% up Data Pion ID π-proton: migration<1% down Data Absorption/decay 20-30% up MC Tertiary Production < 5% down MC Electron Veto Eff ~1% up MC Target-out subtraction ~20% Data

Event Selection Require single, well reconstructed and identified beam particle Downstream trigger in FTP (forward trigger plane) Select beam proton with Beam Cherenkov detectors Electron, pion tagging near 100% 3 σ separation Proton on target within 10 mm of center Angle at target < 5mrad Beam cherenkov detectors

Corrections: Absorption, Decay, Tertiaries Proton interacts in target producing secondary particle Secondary particle decays or interacts before traveling across full detector Upward adjustment ε absorb ( ) Function of theta, p and particle type Tertiary particles ( )

Particle ID Use Time of Flight and Cherenkov detectors to separate π/p TOF system < 3 GeV/c Ckov >3 GeV/c Determine probability particle is π/p based on response of 2 independent PID detectors Pion efficiencies > 95%, migrations all under 1% Gives particle id migration matrix (uniform in θ) Pion Efficiency Proton as π π as proton Proton Efficiency

Harp Data: MiniBooNE Relevance The first goal was to measure π+ production cross sections for Be at p proton = 8.9 GeV/c. Additional measurements include: π - production cross section (for anti-ν running) K + production cross section ( important for intrinsic ν e backgrounds) Thick target secondary yields (effect of reinteractions) No extrapolations in E beam or A, only angle 1.75 λ

HARP Be Results: Dotted line is best fit to Sanford-Wang parameterization

Parametrization of HARP Data HARP data on inclusive pion production fitted to Sanford-Wang parametrization: where: 8.9 Sanford-Wang parametrization used to: Use HARP data in K2K and MiniBooNE beam MC Translate HARP pion production uncertainties into flux uncertainties c1 overall normalization, c2-c5 momentum of π s, c6-c8 angular Compare HARP results with previous results in similar beam momentum, pion phase space range

Comparison to Previous Data Near 12.9 GeV/c:

Spectrometer performance 0.4 0.35 0.3 0.25 momentum resolution momentum calibration: cosmic rays elastic scattering entries 140 120 100 80 π-p PID with de/dx 0.2 60 0.15 40 0.1 0.05 0 0 0.1 0.2 0.3 0.4 0.5 0.6 0. elastic scattering: absolute calibration of efficiency momentum angle (two spectrometers!) PID: de/dx used for analysis TOF used to determine efficiency entries 20 0 70 60 50 40 30 20 10 0 200 400 600 800 1000 1200 1400 1600 de/dx (ADC counts) π-e PID with de/dx 0 200 400 600 800 1000 1200 1400 1600 de/dx (ADC counts)

Large Angle analysis beam momenta: 3, 5, 8, 12 GeV/c beam particle selection and normalization same as previous analysis events: require trigger in ITC (cylinder around target) TPC tracks: >11 points and momentum measured and track originating in target PID selection additional selection to avoid track distortions due to ion charges in TPC: additional selection to avoid track distortions due to ion charges in TPC: first part of spill (30-40% typically of data kept, correction available for future) Corrections: Efficiency, absorption, PID, momentum and angle smearing by unfolding method (same as pc data analysis in forward spectrometer) Backgrounds: secondary interactions (simulated) low energy electrons and positrons (all from π 0 ) predicted from π + and π spectra (iterative) and normalized to identified e +-.

LA and FWD Spectrometers Together Match well

Use focused negative and positive pions NDC4 carbon target (λ=5%) NDC1 NDC2 NDC5 dipole magnet π + 12 GeV/c beam: p, π +, π B 0.4T π - Use negative and positive beams NDC3 Selection of secondary particles (π +, π ) in forward hemisphere using the drift chambers. No of events (pos. beam): 1,000k No of events after cuts: 460k (p+c) 40k (π + +C) No of events (neg. beam): 646k No of events after cuts: 350k (π - +C)

Phase space region New data sets (p+c, π + +C and π +C at 12 GeV/c) Important phase space region covered Data available for model tuning and simulations N2, O2, and Carbon analysed [Barton83] Phys. Rev. D 27 (1983) 2580 [NA49_06] Eur. J. Phys., hep-ex/0606028 HARP (Fermilab) (SPS) (PS)