PoS(ICHEP2020)187 5 10 https://pos.sissa.it/ m space resolution allowing mesons, produced in proton- ` B  decay topology in a few mm range. In addition, about g to B  for the DsTau (NA65) collaboration ∗ [email protected] Speaker ∗ The goal of the DsTauproduction. (NA65) The experiment dominant at source CERN of SPS tau is neutrinos the is decay measurement of of tau neutrino Joint Institute for Nuclear Research, Joliot-Curie 6, Dubna, Russia E-mail: to recognize the peculiar charmed particle decays are expectedphysics, in in particular the to experiment, search for which intrinsic charm makeswere component collected possible in during proton. to 2018 About study pilot 10% run of charm of whole and data the analysis study of and this encouraging sample results isas of ongoing. a the Given new data the experiment analysis, relevance NA65 CERN in hadruns. 2019. approved the The In DsTau project main this data paper, samplepresented. the will status be and collected prospects in 2021-22 of physics NA65 as well as the results of the pilot run are nucleon interactions, to tau neutrinoexperiment and aims tau to lepton measure with further differentialallow to decay cross re-evaluate of DONuT section results tau of reducing lepton. the this systematicsection error reaction. Thus, caused in by the tau the This neutrino tau interaction neutrino measurement cross fluxSuch will uncertainty accuracy of in cross beam section dump measurement experiments will from allowneutrinos. testing 50% the to The Lepton experiment 10%. Flavour exploits Universality for nuclear emulsion detectors with Copyright owned by the author(s) under the terms of the Creative Commons © Attribution-NonCommercial-NoDerivatives 4.0 International License (CC BY-NC-ND 4.0). S. Vasina 40th International Conference on High EnergyJuly physics 28 - - ICHEP2020 August 6, 2020 Prague, Czech Republic (virtual meeting) Experiment DsTau (NA65) — study ofproduction tau at neutrino CERN SPS PoS(ICHEP2020)187 5 10 ∼ S. Vasina beam has g a decays. The g decays in proton- mesons produced → g are not well studied B ± . Such B g 50%). Thus, a new  - a → >  g B a  → − g is quite important for future neutrino B  is mainly decay of proton interaction in the tungsten target. g 8 a and to the decay momenta. Thus, calculation 10 B ×  proton interaction. The analysis of these events 3 2 . 8 2 production by measuring 10 cross section measurements ( g with the further decay a × g g ¯ a a 3 . − 2 g → B −  differential production cross section in the proton interactions, which B 1000 such decays in  ∼ flux prediction for the future neutrino beams with an accuracy below 10%. Then, g . Although there were several measurements on charmed particles, there is a lack a B  flux uncertainty, which is to be improved in the DsTau (NA65) experiment. g a CC cross section measurement with sufficiently low systematic uncertainty will allow testing g The existence of tau neutrino was predicted after the tau lepton discovery in 1975 [1] and it was So far, the tau neutrino interaction cross section was measured by DONuT [3], OPERA [4] and In the accelerator–based neutrino beam source of The DsTau (NA65) experiment studies In addition to the main goal, DsTau (NA65) is able to study charm physics, since a production rate and search for super-nuclei [8]. 2 detected only 25 years later in the DONuT [2] experiment. Still properties of SK [5] experiments under rather differentIn general, conditions, all which the measurements make have the large statistical resultspoor and/or difficult statistics systematic errors to and of compare. experimental 30–50% caused uncertainties. by SHiP, could The provide measurements future with beam–dump negligible experiments, statisticalof errors for the [6]. example, cross Thus, section the in overall suchby accuracy the experiments will be determined by the systematic errors, in particular, Experiment DsTau (NA65) — study of tau neutrino production at CERN SPS 1. Introduction due to quite limited measurements.(CC) In interaction particular, is the known cross with sectionother a of neutrino large tau flavours. statistical neutrino The and charged cross current systematic section uncertaintiesthe measurement Lepton in with Flavour comparison a Universality (LFU) with better of accuracyfor Standard would B-meson Model allow testing decay in asymmetry neutrino (LHCb, interactions. Babar,that Several Belle) may results demonstrate be related hints to of Physics possible Beyond LFU Standard violation Model effects. could allow measuring theangle intrinsic (pseudorapidity) of charm the component charmed particle in pairs,Λ proton the interaction [7] length of by charmed measuring hadrons, the the emission of measurements on the of the tau neutrino fluxsection on the of detector requires the knowledge of the differential production cross measurement of the differential production cross sectionexperiments of as well as for re–evaluation of the DONuT results. nuclear interactions at CERN SPS.spacial DsTau (NA65) resolution exploits allows nuclear recognizing emulsion peculiar techniques. “double-kink” Its topology high of charmed particle pairs are expected in contributes the main uncertainty of the in proton-nucleus interactions: rather large divergence due to the emission angle of project aims to register This goal can be achievedspeed by automatic using scanning stations of developed nuclear in the emulsion, lastindependent two nanometric–precision decades. readout DsTau and (NA65) will high- provide an LFU in neutrino interactions. the PoS(ICHEP2020)187 m. ` , which g S. Vasina ). Second a 0 small kinks.  g or ± →  B  m emulsion layers on both sides. and kink angle of tau lepton is a ` B 2.5 mrad), and detects events, which  ∼ and partner charm ( g decay candidates to find g 3 in the detector. 2 m plastic base with 70 ` momentum is difficult as well due to presence of two B tracks/cm  . Nevertheless, the unique spacial emulsion capabilities and a new 2 5 10 2< tracks/ 6 decays have a very peculiar topology, the decay has “double-kink” and there is 10 g − → 5 B 10  The The main source of background is interactions of secondary hadrons (the products of primary The basic unit of the DsTau detector is shown in1. Fig. It consists of 0.5–mm–thick tungsten A schematic view of experimental setup is shown in1. Fig. The beam profile is measured by a The analysis of the track information accumulated in the emulsion during exposure is done in The automatic scanning systems read and digitize the track information which is similar to the The basic idea of the track reconstruction is a linking of basetracks at the different films a charge or neutral pairevents charm is in quite the challenging interaction because vertex, of1. Fig. short flight However, length reconstruction of of such proton interactions) with no nuclear fragmentsnumber detected. of expected Based background on events the for the FLUKA full [9] data simulation, sample the is abouttarget 18. followed by 10 emulsion plates interleaved with 9 plastic sheets with thickness of 200 Experiment DsTau (NA65) — study of tau neutrino production at CERN SPS 2. Experiment overview few mrad. The measurement of are not detected in theresolution detector. allows identify such Therefore, decay the topologies. useof The about of emulsion 50 emulsion films nm detector provide and a with an position angular nanometric resolution resolution spatial of 0.34 mrad. Each emulsion plate consists of a 210 step is a high precision measurement around the silicon pixel telescope and time profile isby measured a by a target scintillation mover counter. along The Xprimary detector is and protons driven Y with about axes according to counter signal to have uniformtwo steps. distribution First, of scanning of the(HTS) full [10]. emulsion area HTS by has a a fast relatively system, coarse so angular called resolution Hyper ( Track Selector case of any electronic detector. Theat output both of sides the readout of isbasetrack, the the which is emulsion information a on film. basic the unit of trackis information segments These used completed for two for the the further segments whole track are reconstruction. data sample linked The readout collected together in using 2018 pilot the run. according so to called their angles anddensity positions. of In DsTau this task is quite challenging due to high track The combination of 10 basic units formChamber a decay (ECC), module. which It is is followed byECC made so is called of Emulsion used Cloud 26 for charged 1–mm–thickseparators particle in lead momentum the plates front measurement. side interleaved ofis Several by the 12.5 emulsion emulsion x detector plates 10.0 serve plates. with x as 8.6 plastic beam cm. protons tagger. The total size of detector have two decays in a short distance, namely the decays of For this step another scanningresolution of microscope 0.16 with mrad a is used. slower readout More details speed, on but the with scanning systems a are3. high given in angular [11, 12]. Reconstruction and analysis tracking algorithm [12] allow to reconstruct basetracks efficiently. The averaged basetrack finding PoS(ICHEP2020)187 S. Vasina protons analyzed. 6 10 5.0 × ± 34.2 12.7 > Background 155,135 Expected 19.2 ± Signal 80.1 4 115 147,236 Observed 99%. > Vertices in tungsten Double decay topology Statistics found in the sub–sample of 2016, 2018 data related to Schematic view of the “double-kink” event in the basic unit of DsTau decay module (left) and The film-by-film basetrack finding efficiency(left) and the evolution of track density as a function The reconstructed tracks are used to reconstruct vertices, and a systematic search for a decay Table 1: topology of short-lived particles is applied.double decay The topology statistics observed of in the a foundwith vertices sub–sample the and of expectation events the based with on data the the are simulation shown for in the1. Table equivalent It data is sample. consistent efficiency is higher than 95%,part shown in of2. Fig. the detector It due showstracks a with to an slow increase efficiency decrease of of towards the the downstream track density, but it is still high enough to reconstruct Figure 2: of depth in a module (right) [12]. Experiment DsTau (NA65) — study of tau neutrino production at CERN SPS Figure 1: scheme of the experimental setup (right) [12]. PoS(ICHEP2020)187 S. Vasina Phys. Rev. , mesons, which B  Annihilation − 4 + 4 5 Evidence for Anomalous Lepton Production in (1975) 1489. 35 Flight length distributions for charged 1-prong and neutral 2-prong decay candidatesin the double- Lett. DsTau performed test runs in 2016 and 2017 and successfully collected about 10% of full We thank for the support of the beam physicists at CERN for the successful data taking in the This work was supported by JSPS KAKENHI Grant Numbers JP 18KK0085, JP 17H06926, The DsTau experiment studies the tau neutrino production in 400 GeV/c proton interactions [1] M. Perl et al., statistics during 2018 pilot run.physics runs The are experiment planned was for approved 2021–22run by years. as CERN well The SPSC as analysis as preparations of NA65 to the the and data physics the sample run collected are ongoing in successfully. the pilot Acknowledgments proton beam at the SPS north area.technical staff We would from like LHEP to acknowledge Bern. theUniversity precious for We contributions sharing acknowledge of N. the the Naganawa expertise and ofEast the emulsion Technical colleagues University detector. and from Nagoya We University Nagoya who warmly participated thank in students the from beam Middle exposure campaign. and Konica Minolta Science and Technology Foundationand Research project Grant for No. Photographic Science 16 (StudyJINR, of Dubna, the Russia and tau ISS, neutrino Romania.Science production This Foundation in work Ambizione proton-nucleus was interactions) grant partially between PZ00P2_154833, supportedappreciate especially by the the on support Swiss the from National the detector TAEK R&D. of We Turkey and also JINR grant for young scientistsReferences 20-202-02. is important for future neutrinoproton experiments. interactions with The a collected high data statistics. allows to study charm physics in 4. Conclusion and prospects with the tungsten target by measuring the differential production cross-section of Experiment DsTau (NA65) — study of tau neutrino production at CERN SPS Figure 3: charm event samples. The FLUKA MC histograms are area-normalized to data. PoS(ICHEP2020)187 , 02 PoS , (2017) S. Vasina JHEP 10 Phys. Lett. , , (2018) 052006 (2015) 121802 PTEP 98 , 115 (1989) 583-595. (2014) 211. 102 Neutrino Appearance in the 120 Phys. Rev. D g , Phys. Rev. Lett. Hyper–track selector nuclear emulsion , Nuovo Cim. A , (2020) 033 [hep-ex/1906.03487v1] DsTau: Study of tau neutrino production with Measurement of the tau neutrino cross section Discovery of 01 Nucl. Data Sheets 6 , Final tau–neutrino results from the DONuT exper- The FLUKA Code: Developments and Challenges ]. Observation of tau neutrino interactions JHEP , Neutrino physics with the SHiP experiment at CERN Prompt neutrinos and intrinsic charm at SHiP ] hep-ex/0012035 (2008) 052002. ]. 78 (2017) 101. Experimental Proposal, Study of tau-neutrino production at the CERN-SPS Study of hypernuclear production and search for supernuclei in proton-nuclear Phys. Rev. D (2001),[ 218-224 , 504 hep-ex/1507.01417v2 hep-ex/1711.09436 B CNGS Neutrino Beam with the OPERA Experiment iment 400 GeV protons from the CERN-SPS [ 103 [physics.ins-det/1704.06814v3]. CERN-SPSC-2017-029, SPSC-P-354 [hep-ex/1708.08700]. in atmospheric neutrino oscillations with Super-Kamiokande P. R. Sala, G. Smirnov and V. Vlachoudis, for High Energy and Medical Applications interactions in photoemulsion at 70 and 250 GeV readout system aimed at scanning an area of one thousand square meters [ (2019) 077 [hep-ph/1807.02746]. EPS-HEP2017 [2] K. Kodama et al.(DONuT Collaboration), [3] K. Kodama et al. (DONuT Collaboration), [4] N. Agafonova et al.(OPERA Collaboration), [5] Z. Li et al. (Super-Kamiokande Collaboration), [9] T. T. Böhlen., F. Cerutti, M. P. W. Chin, A. Fasso, A. Ferrari, P. G. Ortega, A. Mairani, [8] V.V. Lyukov, [6] M. De Serio (SHiP Collaboration), [7] Weidong Bai, Mary Hall Reno, Experiment DsTau (NA65) — study of tau neutrino production at CERN SPS [11] S. Aoki, et al., [12] S. Aoki et al. (The DsTau/NA65 Collaboration), [10] M. Yoshimoto, T. Nakano, R. Komatani, H. Kawahara,