PoS(NEUTEL2017)078 , c , j , j , m , , c c , r , E. Conti j https://pos.sissa.it/ , , G. Mandrioli , M. Nessi k , G. Brunetti l j , G. Sirri b , b , a a , M. Pozzato o , Y. Kudenko m d , L. Magaletti , G. Collazuol f , M. Mezzetto h s , M. Soldani , p b , C. Brizzolari b , C. Jollet l , E. Wildner , C. Piemonte e c , L. Ludovici , A. Coffani f c , n , A. Meregaglia , M. Bonesini , L. Votano , L. Patrizii i , R. A. Intonti c h o , A. C. Ruggieri , o b q , p , F. Cindolo c , A. Gola , N. Mauri q b , , , P.F. Loverre p a j , E. Vallazza , R. Boanta b , C. Riccio , b l , a a , G. Paternoster j , k , S. Cecchini l , A. Berra , G. De Rosa , A. Longhin ∗ j j b , , V. Mascagna , a , M. Pari k c , E. Radicioni e , F. Terranova b , g , a c [email protected] Copyright owned by the author(s) under the terms of the Creative Commons IPHC, Université de Strasbourg, CNRS/IN2P3, Strasbourg,INFN, France Laboratori Nazionali di Frascati, viaINFN, Fermi Sezione 40, di Frascati (Rome), Roma Italy 1, piazzalePhys. A. Dep. Moro Università 2, di Rome, Bologna, Italy Phys. viale Berti-Pichat Dep. 6/2, Università Bologna, di Italy Milano-Bicocca,INFN piazza Sezione della di Scienza Trieste, 3, via Milano, Valerio, Italy INFN 2 Sezione - di Trieste, Italy Padova, via Marzolo,Phys. 8 Dep. - Padova, Università Italy di Padova, viaINFN Marzolo, Sezione 8 di - Bari, Padova, via Italy Amendola,CERN, 173 Geneva, - Switzerland Bari, Italy Phys. Dep. Università La Sapienza,Fondazione piazzale Bruno A. Kessler Moro (FBK) 2, and Rome, INFN Italy INFN, TIFPA, Trento, Sezione Italy di Napoli, via Cinthia,Phys. 80126, Dep. Napoli, Università Italy degli Studi diInstitute Napoli of Federico Nuclear II, Research via of Cinthia, theCENBG, 80126, Russian Université Napoli Academy de of Bordeaux, Science, CNRS/IN2P3, Moscow, 33175 Russia Gradignan, France Phys. Dep., Università degli studi dell’Insubria,INFN, via Sezione Valeggio di 11, Milano-Bicocca, Como piazza dellaINFN, Scienza Sezione 3, di Milano, Bologna, Italy viale Berti-Pichat 6/2, Bologna, Italy c F. Dal Corso M. Laveder A. Margotti M. G. Catanesi A. Paoloni M. Tenti Attribution-NonCommercial-NoDerivatives 4.0 International License (CC BY-NC-ND 4.0). M. Prest G. Ballerini Fabio Pupilli INFN - Sezione di Padova E-mail: identification in the ENUBET instrumented decay tunnel i j l s r f e c k g h n o p q a b d m PoS(NEUTEL2017)078 ) e 10 ν ∼ (and e ν decays of charged . The Monte Carlo simulation 3 e of the positron tagger in realisticdescribed, conditions together and with a results preliminary on event the reconstruction expected chain signal will selection be efficiency. Speaker. the systematics in fluxes from conventional beams, allowing measuring the The ERC granted ENUBET project aims at developing the technologies to reduce by a factor cross section with a 1% precision, ining the region for of CP interest violation. for future This oscillationthe experiments goal high look- is angle accomplished positron by produced monitoring in in K an instrumented decay tunnel ∗ XVII International Workshop on Neutrino Telescopes 13-17 March 2017 Venezia, Italy PoS(NEUTEL2017)078 layer”). 0 ] foresees a Fabio Pupilli 2 in the beamline is the e ν from and 3 e ]. K 3 . The readout is performed in shashlik 2 . Instrumenting the decay tunnel with fast e ν 0 3 cm π × + e 1 → + k ): 3 e K 20% GeV/c momentum. Its emittance and the radius of the 50 m decays and to provide the reference time of an event (“t 0 ± ]. π 1 ] simulation of the instrumented tunnel has been setup in order to test his 4 and its transverse size is of 3 cross section, which is poorly known in spite of its relevance for precision 0 e ν X surface are displaced below the calorimeter at every 7 cm and are used to suppress 2 3 cm A full GEANT4 [ The ENUBET project is intended to demonstrate the feasibility of this approach; it has been The main limiting factor for a precise measurement of neutrino cross sections is represented by × 2. Simulation of the instrumented decay tunnel and event reconstruction performances in terms of particle identificationgenerated and at to the optimize tunnel his entrance design.rence with design. Secondary emittance More realistic are and distributions momentum willof be distributions the implemented defined focusing as in and soon transfer the as line the refe- ongoing will optimization be completed. calorimetric modules allows the tagging of theof emitted the large electron angle neutrino positrons and flux a [ direct estimation three body decay of charged kaons ( funded by the European Researchtion Council INFN) (ERC for Consolidator Grant, a PI fivesecondary A. year Longhin, duration, beam host starting of institu- from 8.5 Junedecay 2016. tunnel are The optimized reference in designhitting order [ the to instrumented prevent muons walls from oftation pions the allows or tunnel. for undecayed a secondaries The cost-effective from calorimetric and solution efficient for separation the of tunnel instrumen- systematic uncertainties in the assessment ofsimulation the of initial the flux, production that beamline. isexperiments and performed Despite of through ancillary the a measurements use complete ( of intensity,the horn beam hadro-production currents, dump), data the monitoring from precision after dedicated onalso the affects flux prediction the is usually limited to 7-10%. This uncertainty The ENUBET project 1. ENUBET oscillation physics in the nextleptons generation produced of in long-baseline the experiments. decay tunnelficantly The reduce with direct the the monitoring flux-related systematics. of can If overcomeof the these decay secondary limitations tunnel and is signi- short is enough of and the the momentum order of few GeV, the only source of produced in other decaymade modes. of It five, is 15 basedinstruments mm on the units thick, two called iron inner Ultra layers, layers Compactresponds interleaved Modules of to by (UCM) the 4.3 5 calorimeter. mm The thick total plastic length scintillator of tiles, the module that (10 cm) cor- mode through nine WLS fibersmodules coupled with to a longitudinal silicon coarser photomultipliers.the readout calorimeter and Six (every are outer 60 used cm, layers toers measure i.e. of the will shashlik energy release 2.6 released their interaction by energy pions lengths) ina and complete the muons, 3 while two e.m. innermost show- ones.the Rings photon of background two from plastic scintillator pads with Further details on the fullachievements ENUBET of setup, the its first physics year potential, of the the project prototyping can activities be and found the in [ PoS(NEUTEL2017)078 is esti- 2 . 1 Fabio Pupilli (blue). + e ]. The preliminary step is the 5 signals correlated to the seed are (red) and 0 ± π 2 per second), a particle rate of 500 kHz/cm + K 11 10 × ] neural network response for 6 ] (about 5 TMVA [ 1 Figure 1: the ratio among thevisible most energy in energetic all signal layers; in the firstthe electromagnetic fraction of layer energy and released in the the first total layer; the fraction of energy released in the first and secondthe layers; fraction of energy releasedwith in respect the to two the adjacent one longitudinal of rows the in seed; the transversethe plane total visible energy. A multivariate analysis based on a neural network is then applied to the reconstructed events A preliminary event reconstruction chain has been defined [ • • • • • for the discrimination between charged pions and positrons;in it the relies calorimeter on through the pattern five of variables: energy deposit The response of the neural network to pure positron and samples is shown in Fig. mated at the inner surface oflayer the calorimeter. with For a each visible spill, the energythus first exceeding enhancing UCM 20 the in MeV time preselection in is of theclustered positron selected innermost taking events. as into account “seed” UCM their and for position and t therecorded. timing. event The reconstruction, procedure is iterated over all the signals The ENUBET project event building to correlate inbelonging space to the and same time decay, and energy tomeson deal deposits flux with in assumed the different pile-up in induced UCM [ by along other decays; the indeed, tunnel with the PoS(NEUTEL2017)078 Fabio Pupilli 100 40% in ideal conditions ∼ 90 shows the contributions from 3 tagger radius (cm) 80 pads before the seed longitudinal position 0 50% and Fig. conversions in the scintillator). ∼ γ 3 70 no pile-up pile-up included selection efficiency, that amounts to 60 3 e K , the 2 50 40 3 selection efficiency as a function of the decay tunnel radius. In red are shown efficiencies 0 5

Ke

20 15 10 30 25 40 35 -related events: it is required that the three t 0 (%) eff. ke3 π As can be seen in Fig. Additional studies are ongoing to further optimize the tagger, testing different calorimetric As a final step, sequential cuts based on the informations from the photon veto are applied to ]. 3 module granularities and the possibilitymented of fraction reducing of the the number tunnel, of with outer the layers final and/or goal the to instru- asses the systematics to the neutrino flux due when events are temporally separated.at In the black nominal are reported rate. the efficiencies when including pile-up effects mis-identified events. A larger tunnelrequirements radius for is the also focusing beneficial line in and[ terms for of the less radiation stringent hardness emittance properties of the instrumentation Figure 2: and with a tunnel radiusbe of 40 obtained cm, by is enlarging degradedfinal the by tagging pile-up tunnel effects efficiency at to of the below about 20%.conditions 25% expanse the putting of A the purity mitigation a calorimeter can of reduced at the geometrical 1 selection m acceptance, amounts from with to the a beam axis. In these measure an energy inminimum the ionizing particle 0.65-1.7 (thus MeV also suppressing range, compatible with the energy deposit of just one reject The ENUBET project PoS(NEUTEL2017)078 3 e K Fabio Pupilli 400 3) µ 350 (K (Ke3) 0 - µ e ν π π ν 300 Visible energy (MeV) 0 0 + 0 µ 0 ν π π π π π + + + + + + µ π π e µ π 250 4 200 150 100 , JINST 11 no.12, C12040 (2016). , [GEANT4 Coll.], Nucl. Instrum. Meth. A 506, 250 (2003). 50 , these proceedings. , PoS ACAT, 040 (2007). et al. [ENUBET Coll.], CERN-SPSC-2016-036; SPSC-EOI-014. et al. et al. et al. Contribution of the different kaon decay modes to all the events reconstructed as 0 0 et al.

400 200 800 600 1000 decays Reconstructed Figure 3: This project has received funding from the European Union’s Horizon 2020 Research and [5] A. Meregaglia [6] A. Hoecker [4] S. Agostinelli [1] A. Longhin, L. Ludovici and F.[2] Terranova, Eur. Phys.A. J. Berra C 75, 155 (2015). [3] A. Longhin Innovation programme under Grant Agreement no. 654168 and no. 681647. References to the detector response. Acknowledgements The ENUBET project