Ye Yuan

MOMENT: a muon-decay medium-baseline neutrino beam facility

Neutrino beam with about 300 MeV in energy, high-flux and medium baseline is considered a rational choice for measuring CP violation before the more powerful Neutrino Factory will be built. Following this concept, a unique neutrino beam facility based on muon-decayed neutrinos is proposed. The facility adopts a continuous-wave proton linac of 1.5 GeV and 10 mA as the proton driver, which can deliver an extremely high beam power of 15 MW. Instead of pion-decayed neutrinos, unprecedentedly intense muon-decayed neutrinos are used for better background discrimination. The schematic design for the facility is presented here, including the proton driver, the assembly of a mercury-jet target and capture superconducting solenoids, a pion/muon beam transport line, a long muon decay channel of about 600 m and the detector concept. The physics prospects and the technical challenges are also discussed.

Study of tracking efficiency and its systematic uncertainty from J/ψ → pp̅π+π− at BESIII*

Based on J/ψ events collected with the BESIII detector,with corresponding Monte Carlo samples,the tracking efficiency and its systematic uncertainty are studied using a control sample of J/ψ→ppπ~+π~-.Validation methods and different factors influencing the tracking efficiency are presented in detail.The tracking efficiency and its systematic uncertainty for protons and pions with the transverse momentum and polar angle dependence are also discussed.Based on J/ψ events collected with the BESIII detector, with corresponding Monte Carlo samples, the tracking efficiency and its systematic uncertainty are studied using a control sample of J/ψ → ppπ+π−. Validation methods and different factors influencing the tracking efficiency are presented in detail. The tracking efficiency and its systematic uncertainty for protons and pions with the transverse momentum and polar angle dependence are also discussed.

Study of tracking efficiency and its systematic uncertainty from

Based on J/ψ events collected with the BESIII detector,with corresponding Monte Carlo samples,the tracking efficiency and its systematic uncertainty are studied using a control sample of J/ψ→ppπ~+π~-.Validation methods and different factors influencing the tracking efficiency are presented in detail.The tracking efficiency and its systematic uncertainty for protons and pions with the transverse momentum and polar angle dependence are also discussed.Based on J/ψ events collected with the BESIII detector, with corresponding Monte Carlo samples, the tracking efficiency and its systematic uncertainty are studied using a control sample of J/ψ → ppπ+π−. Validation methods and different factors influencing the tracking efficiency are presented in detail. The tracking efficiency and its systematic uncertainty for protons and pions with the transverse momentum and polar angle dependence are also discussed.

J/\psi \to p \overline{p} \pi^+ \pi^-

The experimental muon source (EMuS) is a highintensity muon source at China Spallation Neutron Source (CSNS), aiming to combine SR applications, R&D efforts for a future muon-decay based neutrino beam, and neutrino cross-section measurements. The proton beam has 4 kW of power and is provided by the rapid cycling synchrotron (RCS) of CSNS to a capture system that consists of an adiabatic superconductive solenoid with a maximum field of 5 T and a graphite target located inside the 1st-coil, in order to maximize muons/pions capture and reduce their transverse momentum. In this article we present the challenging target system and the optimization studies that led to the current 4-coils/3-steps design. The challenge arises from the necessary extraction of the spent proton beam along the downstream area of the capture solenoid through a hole, in order to separate it from the muons and pions. In addition, shielding studies are presented in order to examine the effectiveness of the shields on the coils and the low radiation damage expected in the system. INTRODUCTION In this paper, a novel idea of a target station with a stepped superconductive solenoid is presented for the EMuS project at CSNS [1]. The optimization of the design is done in order to facilitate the high energy spent proton beam extraction and also to maximize the capture of both muons and pions. The physics objectives is to explore muon physics (like SR applications) as well as a neutrino beam if possible. In addition, it could act as a R&D platform for MOMENT [2], a muon-decay mediumbaseline neutrino beam facility, which shares similar charge separation and pion transport channel techniques with EMuS. Table 1: CSNS [1,3] Parameters Parameters CSNS-I CSNS-II Beam power (kW) 100 500 RCS Energy (GeV) 1.6 1.6 Beam current ( A) 62.5 315 Repetition rate (Hz) 25 25 Proton per pulse [1013] 1.56 7.8 Linac Energy [MeV] 80 250 EMuS power (kW) 4 20 Bunches per pulse 2 2 Bunch length (ns) 70 70 EMuS LAYOUT The major aims of CSNS is to be among the leading neutron spallation sources internationally and also to operate as large platform for a broad range of high energy physics experiments within its facilities. The CSNS accelerator complex consists of an H Linac of 250 MeV in the final phase, a proton rapid cycling synchrotron (RCS) of 1.6 GeV and beam transport lines, with the ultimate beam power of 500 kW [3]. For EMuS, there is space reserved at the high energy proton experimental area (HEPEA) while a R&D fund has been approved by the National Natural Scientific Foundation of China (NFSC). The protons will be provided to the EMuS target station by RCS. The CSNS parameters are given in Table 1. Figure 1: EMuS schematic layout. Those protons are initially deflected by two dipoles before their entrance into the capture solenoid in order to facilitate downstream the spent protons extraction towards a beam dump. The target station consists of a superconductive solenoid with an adiabatic magnetic field of 5 T maximum. A graphite target is placed inside the solenoid in order to maximize the capture of decay muons and pions along with surface muons1. Downstream, the capture solenoid is connected through a matching solenoid to a bending section responsible for the charge selection, which in turn is connected to the pion decay channel where the surface muons are separated and the neutrino beam is produced. A SR spectrometer is foreseen while the neutrino detector is envisaged 3 meters away from the end of the pion decay channel. A decay muon section is also envisaged from the EMuS layout shown in Figure 1. There are three independent operational beam modes for EMuS, the surface muons (p = 29 MeV/c ± 5%), decay muons (p = 100-200 MeV/c ± 10%) and the neutrino (pπ = 300-500 MeV/c) ones. ___________________________________________ †Vassilopoulos@ihep.ac.cn ____________________________________________ Surface muons are produced on the target surface and produce a beam of maximum spin polarization from positive pions decays at rest, while decay muons are defined as the ones produced from pions decays in the capture solenoid Proceedings of IPAC2017, Copenhagen, Denmark WEPAB127 07 Accelerator Technology T20 Targetry ISBN 978-3-95450-182-3 2871 Co py rig ht

at BESIII

The relative differences in coordinates of Cylindrical Gas Electron Multiplier Detector-based Inner Tracker (CGEM-IT) clusters are studied to search for track segments in CGEM-IT for the BESIII experiment. With the full simulation of single muon track samples, clear patterns are found and parameterized for the correct cluster combinations. The cluster combinations satisfying the patterns are selected as track segment candidates in CGEM-IT with an efficiency higher than 99%. The parameters of the track segments are obtained by a helix fitting. Some χ2 quantities, evaluating the differences in track parameters between the track segments in CGEM-IT and the tracks found in the outer drift chamber, are calculated and used to match them. Proper χ2 requirements are determined as a function of transverse momentum and the matching efficiency is found to be reasonable.

EMuS Target Station Studies

The discovery of the neutrino mixing angle θ13 opens new opportunities for the discovery of leptonic CP violation at high intensity neutrino beams. MOMENT, a future neutrino facility with a high-power proton beam of 15 MW from a continuous-wave linac, is focused on that discovery. The high power of the proton beam causes extreme radiation conditions for the facility and especially for the target station, where the pion capture system of five superconducting solenoids is located. In this paper initial studies are performed for the effects of the radiation on the solenoid structure and the area surrounding it. A concept cooling system is also proposed.

Track segment finding with CGEM-IT and matching to outer drift chamber tracks in the BESIII detector

Considering the aging effects of existing Inner Drift Chamber (IDC) of BESuppercaseexpandafter{romannumeral3}, a GEM based inner tracker is proposed to be designed and constructed as an upgrade candidate for IDC. This paper introduces a full simulation package of CGEM-IT with a simplified digitization model, describes the development of the softwares for cluster reconstruction and track fitting algorithm based on Kalman filter method for CGEM-IT. Preliminary results from the reconstruction algorithms are obtained using a Monte Carlo sample of single muon events in CGEM-IT.

Radiation studies for the MOMENT target station

This paper introduces the calibration of the time-to-distance relation for the BESIII drift chamber. The parameterization of the time-to-distance relation is presented. The studies of left-right asymmetry and the variation with the entrance angle are performed. The impact of dead channels on the time-to-distance relation is given special attention in order to reduce the shifts of the measured momenta for the tracks passing near dead cells. Finally we present the spatial resolution (123 {mu}m) for barrel Bhabha events (|cos{theta}|<0.8) from J/{psi} data taken in 2012.Offline calibration plays an important role in BESIII offline data processing. In order to achieve good spatial and momentum resolution, it is necessary to implement high precision offline calibration for the BESIII drift chamber. This paper studies the time-to-distance relations, which are important calibration constants for track reconstruction. The parameterization of the time-to-distance relation, studies of left-right asymmetry and studies of variation with entrance angle are performed. The impact of dead channels on the time-to-distance relation is given special attention in order to reduce the shift in measured momentum for tracks passing near dead cells. Finally. we present the resolutions for barrel Bhabha events (vertical bar cos theta vertical bar < 0.8) from a J/psi data set taken in 2012. The average spatial resolution is 123 mu m and the momentum resolution for 1.548 GeV/c Bhabha tracks is 11.9 MeV/c.

Study of cluster reconstruction and track fitting algorithms for CGEM-IT at BESIII

Neutrino beam with about 300 MeV in energy, high-flux and medium baseline is considered a rational choice for measuring CP violation before the more powerful Neutrino Factory will be built. Following this concept, a unique neutrino beam facility based on muon-decayed neutrinos is proposed. The facility adopts a continuous-wave proton linac of 1.5 GeV and 10 mA as the proton driver, which can deliver an extremely high beam power of 15 MW. Instead of pion-decayed neutrinos, unprecedentedly intense muon-decayed neutrinos are used for better background discrimination. The schematic design for the facility is presented here, including the proton driver, the assembly of a mercury-jet target and capture superconducting solenoids, a pion/muon beam transport line, a long muon decay channel of about 600 m and the detector concept. The physics prospects and the technical challenges are also discussed.

Calibration study of the X-T relation for the BESIII drift chamber

BESIII experiment adopts a drift chamber as the central tracking detector. Big distortion of the chamber due to mechanical imperfection causes bad momentum resolution. Software alignment is the only possible strategy to estimate the displacements of sub-endplates of the chamber. We have developed an alignment software in the framework of the BESIII Offine Software System. Cosmic-ray data are used in preliminary alignment. The alignment method is introduced in the paper. The results of the alignment are also presented.