The design and basic performance of a Spiral Fiber Tracker for the J-PARC E36 experiment

Abstract

A spiral fiber tracker (SFT) has been designed and produced for the J-PARC E36 experiment as an element of the tracking system for conducting a high-resolution momentum measurement of charge particles from kaon decays. A novel technique to wind the pre-made fiber ribbons spirally was employed for the configuration with four detector layers made of 1 mm diameter plastic scintillating fibers. Good position alignment and sufficiently high detection efficiency for charged particles with minimum ionizing energy were confirmed in cosmic ray test. The tracker was successfully used in the E36 experiment.

Search for Light Neutral Bosons in The TREK/E36 Experiment at J-PARC

“…The possibility to explain anomalies in astrophysics and particle physics [1][2][3] by extending the Standard Model of particle physics (SM) by an additional Uð1Þ D gauge group manifesting itself in a massive gauge boson A 0 (''dark photon'') in the MeV to GeV mass range [4][5][6] motivated a strong activity in theoretical as well as in experimental physics [7][8][9][10][11][12][13][14][15][16]. In a recent work [15], where new physics scenarios were explored as a possible explanation of the proton charge radius problem, the constraints from rare kaon decays were examined.…”

“…1) within the mentioned framework of kinetic mixing (model I) as well as in a model where the A 0 couples only to the muon assuming an explicit breaking of gauge invariance applied in Ref. [14] (model II). In the pioneering experiment [17] of the decay K þ !…”

“…• scintillating fiber target used to stop the incoming kaon beam had a smaller diameter to minimize multiple scattering and energy loss of the outgoing decay particles [2] • addition of Spiral Fiber Tracker [2,14] • redundancy in particle ID systems used to distinguish between e and µ with high efficiency and low misidentification probability [2] • faster readout electronics of the CsI(Tl) calorimeter with a pile-up capable data acquisition system using FPGA based waveform digitization [2,15].…”

“…The incoming K + was tagged with a Fitch Čerenkov detector [2], in order to distinguish it from a π + , before stopping and decaying at rest in the active target, a matrix of 256 scintillating fibers oriented longitudinally along the beam, which determines the location of the kaon stop in the transverse plane. Surrounding the target was the a Spiral Fiber Tracker (SFT), which consisted of two pairs of fiber layers spiraling in left/right helicity and provided the z-coordinate of the of the outgoing decay particle(s) [14]. The target-SFT system was surrounded by 12 timeof-flight counter (TOF1) and 12 aerogel Čerenkov counters (AC) aligned with the 12 sectors of the toroidal spectrometer.…”