PoS(EPS-HEP2019)434 charmed ) 5 https://pos.sissa.it/ 10 ( O cross section mea- CC interactions. It τ flux estimation. The τ ν τ ν ν beam is by the sequential τ ν studies. A precise measurement τ ν double kinks in a few mm range. During X differential production cross section (especially → s τ D → s D differential production cross section in fixed target experiments s D interactions will be collected in the tungsten target, and 1000 8 10 observations. The practical way of producing a × τ ν for the DsTau Collaboration mesons produced in high-energy proton interactions. However, there is no experi- ∗ s cross section would enable a search for new effects in D decays will be detected. In addition to the primary aim, the analysis of τ ν τ → production aiming at providing important data for future [email protected] s τ Speaker. mental measurement of the of the also has practical importance for theand next astrophysical generation experiments for oscillationdecay studies of using proton beams, which leads to a large systematic uncertainty on the DsTau is an experiment at theν CERN SPS, approved by CERN in June 2019 as NA65, to study DsTau experiment aims to reduce the systematicsurement uncertainty to in 10% the or current below, by measuring the longitudinal dependence). For this purpose, emulsion detectorswill with be a spatial used resolution allowing of the 50 nm detection of the physics runs, 2.3 particle pairs can provide valuable by-productsand such the as intrinsic studies charm of the contentpresented forward in together charm with proton. production a prospect Results for the from physics the runs test in 2021 runs and and 2022. the pilot run will be D ∗ Copyright owned by the author(s) under the terms of the Creative Commons c Attribution-NonCommercial-NoDerivatives 4.0 International License (CC BY-NC-ND 4.0). Tomoko Ariga Kyushu University E-mail: NA65/DsTau: Study of -neutrino production at the CERN SPS European Physical Society Conference on High10-17 Energy July, Physics 2019 - EPS-HEP2019 - Ghent, Belgium PoS(EPS-HEP2019)434 n ] but 6 decays. . More- 1 e interaction τ cross section → Tomoko Ariga ] and Hyper- ν τ 2 τ is necessary for ν ] and SK [ ]. The dominant 10 s 5 9 mesons produced , D SM 8 ± s 9 D 8 is transverse momentum. differential production cross ], OPERA [

T s 4 DONuT 7 n p D interactions with n=6.1 from Pythia 6 τ CC cross section has also a practi- 6 ν τ ν 5 4 0

60 40 20 80

] at CERN, it is expected to collect thousands

120 100 τ

ν cm 10 ( 7 /GeV)

× σ 2 const -40 is Feynman x and 1 in formula (1). Right: The cross section result from the F

x n

not included) not

(main systematic uncertainty systematic (main SM DONuT with n=6.1 from Pythia 6 Pythia from n=6.1 with DONuT

CC cross section would be interesting to test the τ DONuT τ ν ν (1), where 2 T ’s that pass through the detector. Conventionally, the differential µ τ bp ν ν − e flux measurements. The systematic uncertainty from the n ], there is a lack of measurements on the ) e e . This has been the main source of the uncertainty of the | ] and accelerator neutrino experiments such as DUNE [ ν ν n 1 10 F x ]. charged-current (CC) cross section is known with much larger statistical and flux uncertainty, which will be studied by this experiment [ 4 0 averaged cross section of the three neutrino flavors. For the DONuT’s result, the value

τ − |

80 60 40 20 τ

120 100

ν

1 cm 10 (

/GeV) ν ν

× σ

2 ( const -40 , ] rely on ν 3 ∝ in the accelerator-based neutrino beam is leptonic decays of 2 T interaction cross section was only measured in DONuT [ τ measurements in future experiments. τ ν Left: dp ν τ F ν to estimate the flux of are the parameters controlling the longitudinal and transverse dependence of the differential interactions, providing a negligible statistical uncertainty in the cross section measurement. dx s The There are only a few measurements for tau and their properties are not well studied. b / τ D ν σ 2 section in 400 GeV protonsented interactions, by especially the concerning parameter the longitudinalmeasurements. dependence A repre- new measurement of differential production cross section of Figure 1: is plotted in the empiricalDONuT range experiment of [ the parameter Kamiokande [ with large statistical and/or systematicalmental uncertainties uncertainties. of In 30-50% a due future to experimentof low SHiP statistics [ and experi- Thus the overall uncertainty of the crossespecially section by will the be determined by the systematic uncertainties, precise In particular, the NA65/DsTau 1. Study of tau neutrinos systematical uncertainties compared toover, the a other precise neutrino measurement flavors, of as the shown in Figure cross section could be a limiting factor in their analyses due to source of in proton-nucleus interactions. Itof is necessary to know the differential production cross section and production cross section, respectively. Although therecles were as several summarized measurements in on [ charm parti- universality in neutrino scattering. The measurement of the production cross section ofd charmed particles is approximated by a phenomenological formula cal impact on current andin future Super-Kamiokande [ experiments. Mass hierarchy measurements PoS(EPS-HEP2019)434 ], the . With 11 2 charmed ) 5 flux will be Tomoko Ariga τ 10 ν ( O events appears as a X → τ → s D as a function of the number of detected n production in 400 GeV proton-nucleus production will be performed by detect- s τ D ν could be estimated. The expected precision production, a high yield of n τ ν 2 proton interactions with the tungsten target. 8 10 × m-thick tungsten plate as a target followed by 10 emulsion µ detected events, the relative uncertainty of the (left). In addition, another decay of a charged/neutral charmed X 3 → m-thick plastic sheets which act as a decay volume for short-lived decays in 2.3 τ µ X → s → D τ as a function of the number of detected events is shown in Figure decays following high-energy proton-nucleus interactions. The project aims to n → s X D events. → τ X Expected precision for the measurement of parameter 1000 → → ∼ s τ In addition to the primary aim of studying DsTau will provide a differential cross section of The basic unit is made of a 500- The principle of the experiment is to detect the topology of In the DsTau experiment, a direct measurement of D → s interaction, which can bephenomenological directly formula implemented (1), and in theof future parameter the experiments. parameter It could be fit withreduced to the below 10%. particle pairs is expected.as measurements The of analysis the of forward charm those production, events the can intrinsic provide charm valuable content in by-products, proton such [ double-kink as shown in Figure particle will be observed with atopology in flight a length short of distance a is few a millimetres. very peculiar Such signature a of double-kink thisfilms plus process. decay interleaved with 200- particles as well as high-precisionby particle the trackers. so-called Emulsion A Cloud module ChamberThe comprises for whole ten momentum detector such measurement module units of is followed theof 12.5 daughter 131 cm emulsion particles. wide, films. 10 During cmGeV the high proton physics beam. and runs, a 8.6 total cm of thick 370 and modules consists will of be a exposed to total the 400 detect Figure 2: 3. The DsTau detector the statistics of 1000 D ing NA65/DsTau 2. Physics goals interaction cross section of charmed hadrons. PoS(EPS-HEP2019)434 ). X → τ . Events δθ 5 , ] to detect τ 13 → Tomoko Ariga s D (right)) are then δθ 3 . The resolution is estimated to s /hour/layer, which is the fastest D 2 P ) and kink angles ( τ . It is consistent with the prediction. 1 FL , S (middle) shows the detector setup at the H4 D 3 FL 3 1 prong events is estimated by PYTHIA simulation → τ production following high energy proton interactions, will → τ experiments and pave a way for the search of new physics s ν τ D ν will be reconstructed by means of a machine-learning algorithm s D ] with the readout speed of 0.45 m 12 . The statistics of the found vertices and events with the double decay topology 4 –nucleon CC interactions. The letter of intent and proposal of DsTau were reviewed τ ν Left: Schematic view of the basic unit. Middle: Detector setup for the test beam at the CERN decays. τ 2 cm by tuning the beam optics. Two test runs were conducted at the CERN SPS H2 and H4 beam lines in 2016 and 2017 to The DsTau experiment will study The event analysis is based on readout of the full emulsion detectors by the Hyper Track The detection efficiency for the → × s test and improve the detectorcollecting structure 10% and of exposure the scheme. full In statistics collected. 2018, Figure a pilot run was conducted, be 20%. 4. Results from the test runs and the pilot run The combination of these four variables provides an estimate of system at present. Readoutthe of total emulsion will films be from finished theused by pilot to the run find end vertices. is of A in systematic 2019.to progress search the and The for reconstructed about the reconstructed vertices. 86% decay tracks Events of topology (Figure decay with of are a short-lived selected. particles charged is An particle applied example decayshown of and in double another charm Figure charged event or candidate neutral found by this analysis scheme is with decay topologies will beD further analyzed by dedicated high-precision systems [ 5. Summary and prospects provide essential inputs for future effects in observed in a sub-sample of the data are shown in Table by CERN-SPSC. DsTau was then approved by CERN in June 2019 as NA65. NA65/DsTau beamline. To have uniformcm irradiation of the detector, the beam spot was enlargedSelector to (HTS) roughly system 1 [ The decay length distribution of the data and the FLUKA simulation is shown in Figure Figure 3: SPS H4 beamline. The modulebeam. was driven Right: by 3D a display target of mover the so reconstructed that tracks. it was uniformly exposed to the proton to be 20%. The momentum of using topological variables such as flight lengths ( PoS(EPS-HEP2019)434 Tomoko Ariga 10000 m) µ 0.3 9000 ± 8000 2.4 Flight length ( 7000 area normalized Background 910 (syst) 6000 Data FLUKA MC ± 5000 Expected Neutral 2 prong decay 3.2 4000 ± 3000 28390 Signal 2000 13.5 neutral decay 1000 0 1 6 5 4 3 2 0 7 CC cross section measurement can be sufficiently 4 kink 19 τ ν 29 297 flux prediction for future experiments with accuracy 10000 m) Observed µ τ primary vertex ν 9000 8000 Flight length ( 7000 area normalized 6000 m FLUKA MC Data 400 GeV proton 5000 Charged 1 prong decay 500 µ 4000 3000 2000 ]. 1000 10 0 Vertices in tungsten 8 6 4 2 0 10 ]. Double decay topology ]. 10 10 A double charm candidate event with a neutral 2-prong (vee) and a charged 1-prong (kink) topol- Flight length distributions for charged 1-prong and neutral 2-prong decay candidates in the double- Statistics found in the sub-sample of data in which 5 629 670 are analyzed in one unit (1 The test runs in 2016-2017 and the pilot run in August 2018 were performed, in which we We would thank for the support from the beam physicists at CERN and the SPS coordinator. charm event samples [ accumulated over 20 million proton interactionssamples in are the in detector. progress. The The readout resultsin and provide 2021 a analysis and proof of of 2022. these theunder feasibility DsTau 10%. will of The the provide systematic full-scale a uncertainty physics of runs the Figure 5: We acknowledge the technical staffs fromsharing LHEP Bern, the the expertise colleagues from of Nagoyafrom emulsion University Middle for detector, East Technical and University those andJSPS from who KAKENHI Nagoya Grant helped University. Numbers This the JP work 18KK0085 beam was and exposure supported JP by campaign 17H06926. Table 1: tungsten plate) [ reduced. Acknowledgments Figure 4: ogy (tilted view) [ NA65/DsTau PoS(EPS-HEP2019)434 ratio, e ν / τ µ ν ν Tomoko Ariga 5 track reconstruction in nuclear emulsion detectors based on GPU π Phys. Let. B 433 (1998) issue 1, p. 9. Underground Neutrino Experiment (DUNE): Volume 1:-DESIGN-2016-01 The (2016). LBNF and DUNE Projects, oscillation experiment using a J-PARC neutrino053C02. beam and Hyper-Kamiokande,PTEP 2015 (2015) Phys. Rev. D 78 (2008) 052002. Appearance in the CNGS Neutrino Beam,Rev. Lett. Phys. 121 Rev. Lett. (2018) 120 no.13, (2018) 139901. no.21, 211801. Erratum: Phys. atmospheric neutrino oscillations with Super-Kamiokande, Phys. Rev. D 98, 052006 (2018). SPS, CERN-SPSC-2015-016, SPSC-P-350 (2015). CERN-SPS, CERN-SPSC-2017-029, SPSC-P-354. (2019) 240. from the CERN-SPS, J. High Energ. Phys. 2020 (2020) 33. system aimed at scanning an area of one thousand square meters, PTEP 10technology, (2017) JINST 103. 9 (2014) P04002. [2] R. Acciarriet al.[DUNE Collaboration], Long-Baseline Neutrino Facility (LBNF) and Deep [3] K. Abeet al.[Hyper-Kamiokande Proto-Collaboration], Physics potential of a long-baseline neutrino [4] K. Kodama et al. [DONuT Collaboration], Final tau-neutrino results from the[5] DONuT experiment, N. Agafonova et al. [OPERA Collaboration], Final Results of the OPERA Experiment on [6] Z. Li et al. [Super-Kamiokande Collaboration], Measurement of the [7] cross section in M. Anelliet al. [SHiP Collaboration], A facility to Search for Hidden[8] Particles (SHiP) atS. theCERN Aoki et al. [DsTau Collaboration], Experimental Proposal, Study of tau-neutrino production[9] at the T. Ariga [DsTau Collaboration], Study of tau-neutrino production at the CERN SPS, PoS ICHEP2018 [1] Y. Fukudaet al.[Super-Kamiokande Collaboration] Measurement of a small atmospheric [10] S. Aoki et al. [DsTau Collaboration], DsTau: study of tau neutrino production[11] with 400Weidong GeV Bai, protons Mary Hall Reno, Prompt[12] neutrinos andM. intrinsic Yoshimoto, charm T. at Nakano, SHiP, R. arXiv:1807.02746. Komatani, H. Kawahara, Hyper-track selector nuclear emulsion[13] readout A. Ariga and T. Ariga, Fast 4 NA65/DsTau References