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NA6/SHINE: Hadron Production for DUNE
Alysia Marino, University of Colorado Boulder DUNE Collaboration Spectrometer Pre-Meeting, May15, 2017
NA61/SHINE @ CERNSPS Heavy Ion and Neutrino Experiment located in the North Area at CERN
‣ Fixed target experiment ‣ Primary 400 GeV/c proton beam, Secondary beams from ~26A
to 160A GeV/c
2
A π+ + C event
Rich physics program includes ‣ heavy ion physics ‣ hadron production for
neutrino beams ‣ cosmic ray production
NA61/SHINE Detector
• Comprises several large acceptance TPCs, first two inside magnets
• In summer 2017 Adding two new TPCs in forward direction
‣ Allows for better tracking and dE/dx separation for forward particles 3
FTPC1 FTPC2/3 PSD
ToF-F
Top View
NA61/SHINE and T2KNA61 Has made a number of measurements of 31 GeV/c protons on thin and full-scale replica carbon targets that are highly relevant for T2K, including ‣ Eur.Phys.J. C76 (2016) no.2, 84 (Thin C
target measurements of π,κ,Λ,p production)
‣ Eur.Phys.J. C76 (2016) no.11, 617 (π yields from T2K replica target)
Thin target π uncertainties ~5%, K uncertainties 10%; current full target π uncertainties ~4% in most bins
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5 10
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1.52 < 420 mradθ360 <
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Data 2009
FTF_BIC - G495
QGSP_BERT - G410
p [GeV/c] p [GeV/c]
p [GeV/c]
p [GeV/c]
]-1
) [(ra
d.G
eV/c
)θ
n/(d
pd2 d
]-1
) [(ra
d.G
eV/c
)θ
n/(d
pd2 d
2 4 6 8
Fig. 27: (Colour online) Laboratory momentum distributions of p+ mesons produced in p+C interactions at 31 GeV/c in differentpolar angle intervals. Distributions are normalized to the mean p+ multiplicity in all production p+C interactions. Vertical bars showthe statistical and systematic uncertainties added in quadrature, horizontal bars indicate the size of the momentum bin. The overalluncertainty due to the normalization procedure is not shown. The spectra are compared to predictions of the FTF_BIC-G495 andQGSP_BERT-G410 models. Ref. [56] shows predictions for all models considered in Sec. 6.
Estimated DUNE Flux Uncertainty
Dominated at low energies by π/K reinteractions and p interactions not covered by existing data, and at medium energy by uncertainties on existing pion production data 5
hadro-production, elastic, and quasi-elastic cross-sections. Estimates of the uncertainty on
the DUNE ⌫µ flux using the multi-universe statistical method developed by the MINER⌫A
experiment are approximately 8% in the focusing peak [2], with uncertainties on the near/far
flux ratio of 1-2% – see Figure 3.
Figure 3: Estimated uncertainties on the neutrino flux at the DUNE far detector (left) and onthe ratio between the near and far detectors (right), assuming the 2-horn optimizeddesign described in [1].
Although this is the most advanced procedure available for estimating flux uncertain-
ties, it relies on guesses to how wrong models of unmeasured differential hadro production
and elastic scattering cross sections may be. It also does not take into account the possibility
of substantial mistakes in the beam simulation which could cause inaccuracies at the level
of tens of percent. Issues such as overly simplified horn shape models, ommisions of cool-
ing water, and unsimulated shifts in the horn positions have been recently discovered in the
NuMI beam simulation. DUNE should be prepared for the possibility of similar problems.
The 1-2% precision of the flux spectromter concept would be a substantial improvement over
the current uncertainty estimate of 8%. Moreover, it would correct many of the potential
simulation inaccuracies that are not accounted for in this estimate.
The impact of the spectrometer measurement on the overall DUNE sensitivities is difficult
to determine at this time, as it requires a complete and detailed simulation of the analysis.
The only tool for estimating sensitivities available at the time of this writing is the GLoBES
configuration used for figures in the DUNE CDR, such as those shown in Figure 4. These
show the projected sensitivity of the experiment to CP violation and the mass hierarchy as a
3
L. Fields, DUNE Collab Meeting,
Sept 2016
NA61/SHINE and DUNEEffort in the US to make a suite of measurements of hadron production at energies and on targets relevant for DUNE and other Fermilab experiments ‣ Measure primary 60-120 GeV/c proton interactions
on potential target materials (graphite and Be) from ‣ Measure interactions of secondary pions and kaons
from 30-60 GeV/c on target and horn materials (graphite, Be, and Al)
6
pp
π+
π+ p
π+
US NA61
University of Colorado: Scott Johnson, Alysia Marino, Yoshikazu Nagai, Brant Rumberger, Eric Zimmerman Fermilab: Alberto Marchionni Los Alamos National Laboratory: Geoff Mills University of Pittsburgh: Christian Farina, Ben Messerly, Vittorio Paolone, Athula Wickermansinghe
7
Secondaries in DUNE
• DUNE secondaries are well-matched to NA61 acceptance
8
Momentum (GeV/c)0 20 40 60 80 100
Angl
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rad)
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024681012141618
-610×µν producing +π
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-610×µν producing +π
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012345678
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Momentum (GeV/c)0 20 40 60 80 100
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rad)
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00.10.20.30.40.50.60.70.8
-610×µν producing +K
Momentum (GeV/c)0 20 40 60 80 100
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00.511.522.533.54
-910×eν producing +K
DUNE secondary π+
DUNE secondary K+
NA61 Acceptance 4.6 Tm Field
NA61 Acceptance 9.0 Tm Field
120 GeV Reference Beam
Data Sets Taken for Fermilab ν Experiments 2012-2016
Can’t measure spectra, but will measure overall production cross section from these datasets. Analysis in progress for most of these.
9
Data Type Year triggers Detector
p + C @ 120 GeV/c 2012 1M,2.8M
No magnets,No VTX1 magnet
π+ + C @ 31GeV/c 2015 745k No magnets
π+ + Al @ 31GeV/c 2015 565k No magnets
p + C @ 31GeV/c 2015 388k No magnets
π+ + C @ 60GeV/c 2015 577k No magnets
π+ + Al @ 60GeV/c 2015 535k No magnets
K+ + C @ 60GeV/c 2015 506k No magnets
K+ + Al @ 60GeV/c 2015 339k No magnets
Running in 2016 Magnet repaired in May 2016.
10
Data Type triggers Comment
p + C @ 120 GeV/c 4.3 M Fall 2016, with magnets
p + Be @ 120 GeV/c 2.2 M Fall 2016, with magnets
p + C @ 60 GeV/c 2.9 M Summer 2016, with magnets
p + Al @ 60 GeV/c 3.2 M Fall 2016, with magnets
p + Be @ 60 GeV/c 2.1M Fall 2016, with magnets
π+ + C @ 60GeV/c 4.2 M Fall 2016, with magnets
π+ + Be @ 60 GeV/c 2.6 Fall 2016, with magnets
Running in 2017-18
5.5 Weeks of running approved this fall. Will make a similar request for 2018. Additional thin target running under consideration: ‣ Run 120 GeV p+C and p+Be with new FTPCs ‣ 90 GeV p+C‣ 60 GeV π+
+ Al
‣ 30 GeV π+ + C , (TOFs)‣ 60 GeV π- + C ‣ 60 GeV K+ + C
In 2018, possibly NOvA replica target11
Beyond 2018
No beam for SPS in 2019 or 2020 (LHC Long Shutdown #2) NA61/SHINE is formulating a plan for running after 2020 If available in 2021 or 2022, prototype targets for the LBNF beam might make sense
12
Long Target RunningT2K Long target data on π+- published in Eur.Phys.J. C76 (2016) no.11, 617 Update with more statistics and more species coming later this summer
13
T2K Replica Target Binning
T2K target is 90 cm long (1.9 nucl. int. lengths) 6 bins: 1-5 are 18 cm slices of target, last bin is the downstream face Track extrapolated backward to determine where it exited target. Point of closest approach used if no intersection and within 1σ of target surface
14
Systematics 0 - 60mrad
Backward extrapolation (red) dominates in most upstream bin, up to 10% at small angles
15
617 Page 12 of 27 Eur. Phys. J. C (2016) 76 :617
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p [GeV/c] p [GeV/c] p [GeV/c] p [GeV/c] p [GeV/c] p [GeV/c]
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<140θ100< Z 6
p [GeV/c] p [GeV/c] p [GeV/c] p [GeV/c] p [GeV/c] p [GeV/c]
rela
tive
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rtain
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tive
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rtain
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tive
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rtain
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Fig. 14 Components of the systematic uncertainties for positively charged pion spectra, in the polar angle range from 0 to 140 mrad, and for thesix longitudinal bins as a function of momentum
ToF-F acceptance but not having a recorded hit in the ToF-Fdue to decay and due to absorption or interactions of pionswith the detector. The corrections related to the decay arecomputed via the precisely known pion decay which shouldbe model independent. Hence, when varying the number ofrequested measured points in the MTPCs, one does not expect
to see differences in the final spectra. Any variations wouldrepresent an uncertainty due to imperfections in the descrip-tion of the spectrometer which can introduce a difference inthe acceptance and reconstruction efficiency (merging tracksegments between VTPC-2 and MTPC-L/R) between sim-ulated and real data. This uncertainty decreases fast with
123
Systematics - 60-140 mrad
Smaller effect at larger angles, but backward extrap still dominates upstream bins
16
617 Page 12 of 27 Eur. Phys. J. C (2016) 76 :617
0.05
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<40θ20< Z 2
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<20θ0< Z 4
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0 10 20 10 20 10 20 10 20 10 20 10 20
PIDFeed-downrec.efftof.eff
lossπback extrapTotal
<60θ40< Z 6
p [GeV/c] p [GeV/c] p [GeV/c] p [GeV/c] p [GeV/c] p [GeV/c]
rela
tive
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rtain
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0 2 4 6 8 2 4 6 8 2 4 6 8 2 4 6 8 2 4 6 8 2 4 6 8
PIDFeed-downrec.efftof.eff
lossπback extrapTotal
<140θ100< Z 6
p [GeV/c] p [GeV/c] p [GeV/c] p [GeV/c] p [GeV/c] p [GeV/c]
rela
tive
unce
rtain
ties
rela
tive
unce
rtain
ties
rela
tive
unce
rtain
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Fig. 14 Components of the systematic uncertainties for positively charged pion spectra, in the polar angle range from 0 to 140 mrad, and for thesix longitudinal bins as a function of momentum
ToF-F acceptance but not having a recorded hit in the ToF-Fdue to decay and due to absorption or interactions of pionswith the detector. The corrections related to the decay arecomputed via the precisely known pion decay which shouldbe model independent. Hence, when varying the number ofrequested measured points in the MTPCs, one does not expect
to see differences in the final spectra. Any variations wouldrepresent an uncertainty due to imperfections in the descrip-tion of the spectrometer which can introduce a difference inthe acceptance and reconstruction efficiency (merging tracksegments between VTPC-2 and MTPC-L/R) between sim-ulated and real data. This uncertainty decreases fast with
123
DUNE long target
For a 2-m long DUNE target, backward extrapolation likely to be a serious issue. Will likely need to run with target at least partially inserted into vertex TPC1 Will soon begin MC studies to understand acceptances in this configuration
17
18
Summary
NA61/SHINE experiment at CERN is taking thin target data of hadron production that is highly relevant for the LBNF beamline Currently focussed on thin target measurements, to be as flexible as possible for future target options Beyond 2020, the biggest impact could be from DUNE replica targets.
19
Backup
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5 10 15 20
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0.1 < 40 mradθ20 <
- tof-dE/dx+π Total sys. PIDFeed-down Track cutsRec. algo Rec. tofK-Fixed Fwd. Acc.Fr
actio
nal e
rror
p [GeV/c]Fig. 16: (Colour online) Breakdown of systematic uncertainties of p+ spectra from the tof -dE/dx analysis, presented as a functionof momentum for the [20,40] mrad angular interval.
5 10 15 20 25
0.05
0.1 < 40 mradθ20 <
- tof-dE/dx-π Total sys. PIDFeed-down Track cutsRec. algo Rec. tof
weightΛ Fwd. Acc.Frac
tiona
l err
or
p [GeV/c]Fig. 17: (Colour online) Breakdown of systematic uncertainties of p� spectra from the tof -dE/dx analysis, presented as a functionof momentum for the [20,40] mrad angular interval.
as a conservative limit to this source of systematic uncer-tainty.
(vi) Secondary interactions and non-L feed-down corrections.As in the case of the dE/dx (Section 4.5) and h� (Sec-tion 4.6) approaches, the important contribution to the sys-tematic uncertainty at low momenta comes from the uncer-tainty of the simulation-based correction for secondary in-teractions and weak decays of strange particles (excludingL hyperons). Following arguments described in Ref. [5] anuncertainty of 30% of the correction value was assigned forboth of these sources.
(vii) L feed-down correction. The correction for the feed-downto pions and protons originating from L decays was cal-culated separately based on measured L spectra (see Sec-tion 4.4.1). The uncertainty assigned to this correction wasestimated to be 30% which is an upper limit on the overalluncertainty of the measured L spectra.
Figures 16 and 17 show a breakdown of the total systematic un-certainty in the tof -dE/dx analysis for the example of the angu-lar interval [20,40] mrad.
4.5 The dE/dx analysis method
The analysis of charged pion production at low momentumwas performed using particle identification based only on mea-surements of specific energy loss in the TPCs. For a large frac-tion of tracks tof can not be measured since the majority of low-momentum particles does not reach the ToF-F detector. A reli-able identification of p+ mesons was not possible at momentaabove 1 GeV/c where the BB curves for pions, kaons, and pro-tons cross each other (see Fig. 5). On the other hand, since thecontamination from K� and antiprotons is almost negligible forp� mesons, the dE/dx analysis could be performed for momentaup to 3 GeV/c allowing consistency checks with the other iden-tification methods in the region of overlap.
The procedure of particle identification, described below, istailored to the region where a rapid change of energy loss withmomentum is observed. This procedure was used already for the2007 data and more details can be found in Ref. [52]. Here justthe most important steps of the analysis are described.
In order to optimize the parametrization of the BB function,samples of e±, p±, K±, p, and d tracks with reliable particleidentification were chosen in the bg range from 0.2 up to 100.The dependence of the BB function on bg was then fitted tothe data using the Sternheimer and Peierls parametrization ofRef. [53]. This function was subsequently used to calculate for
22
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0.4 +π < 100 mradθ60 < 2007 stat. error2007 syst. error
2009 stat. error2009 syst. error
p [GeV/c]
Frac
tiona
l Err
ors
Fig. 24: (Colour online) Comparison between NA61/SHINE statistical and systematic uncertainties obtained using the 2007 [5] andthe 2009 datasets in a selected angular interval [60,100] mrad for p+.
5 10 15 20
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0.3 -π < 100 mradθ60 < 2007 stat. error2007 syst. error
2009 stat. error2009 syst. error
p [GeV/c]
Frac
tiona
l Err
ors
Fig. 25: (Colour online) Comparison between NA61/SHINE statistical and systematic uncertainties obtained using the 2007 [5] andthe 2009 datasets in a selected angular interval [60,100] mrad for p�.
proton spectra are in a good agreement with preliminary resultsobtained using the 2007 data [58].
5.4 V 0 results
The K0S and L spectra are shown in Fig. 32 and Fig. 33 and
numerical results are given in Tables 9 and 10, respectively. Asexplained in Section 4.4.1, those measurements are used to re-duce the dominant systematic uncertainties due to the feed-downcorrection in the charged hadron analyses. Results are consis-tent within the quoted systematic uncertainties with previouslypublished measurements [14] which were obtained with a muchcoarser {p,q}binning due to the lower statistics of the 2007data.
The spectra of K0S can be cross-checked by measurements of
K± yields, thanks to the unique capability to measure these threetypes of kaons simultaneously in the NA61/SHINE experiment.So far, only a few experiments have been able to perform suchmeasurements and to test two different theoretical hypothesesthat predict K0
S yields from K± production rates giving incon-
clusive results. The first approach assumes isospin symmetry inkaon production and predicts (see e.g. Ref. [59]):
N(K0S ) =
12(N(K+)+N(K�)) . (27)
The second method uses a quark-counting argument [60], witha simplified quark parton model. The following assumptions aremade on the number of sea and valence quarks:
us = us = ds = ds, ss = ss , (28)n ⌘ uv/dv . (29)
Taking into account that interactions are with a carbon nucleus(n = 2 for p+p collisions, n = 1 for p+n), the relation betweenmean multiplicity of K0
S , K+ and K� is:
N(K0S ) =
18(3N(K+)+5N(K�)) . (30)
The second method is currently used to tune K0L production in
the T2K flux simulation chain [17]. Figure 32 shows a com-parison of the measured spectra of K0
S to the predictions from