ATLAS Collaboration(Aaboud, M. et al), Alvarez Piqueras, D., Aparisi Pozo, J. A., Bailey, A. J., Barranco Navarro, L., Cabrera Urban, S., et al. (2019). Electron and photon energy calibration with the ATLAS detector using 2015-2016 LHC proton-proton collision data. J. Instrum., 14, P03017–60pp.
Abstract: This paper presents the electron and photon energy calibration obtained with the ATLAS detector using about 36 fb(-1) of LHC proton-proton collision data recorded at root s = 13 TeV in 2015 and 2016. The different calibration steps applied to the data and the optimization of the reconstruction of electron and photon energies are discussed. The absolute energy scale is set using a large sample of Z boson decays into electron-positron pairs. The systematic uncertainty in the energy scale calibration varies between 0.03% to 0.2% in most of the detector acceptance for electrons with transverse momentum close to 45 GeV. For electrons with transverse momentum of 10 GeV the typical uncertainty is 0.3% to 0.8% and it varies between 0.25% and 1% for photons with transverse momentum around 60 GeV. Validations of the energy calibration with J/psi -> e(+)e(-) decays and radiative Z boson decays are also presented.
|
Poley, L., Blue, A., Bloch, I., Buttar, C., Fadeyev, V., Fernandez-Tejero, J., et al. (2019). Mapping the depleted area of silicon diodes using a micro-focused X-ray beam. J. Instrum., 14, P03024–14pp.
Abstract: For the Phase-II Upgrade of the ATLAS detector at CERN, the current ATLAS Inner Detector will be replaced with the ATLAS Inner Tracker (ITk). The ITk will be an all-silicon detector, consisting of a pixel tracker and a strip tracker. Sensors for the ITk strip tracker are required to have a low leakage current up to bias voltages of 500V to maintain a low noise and power dissipation. In order to minimise sensor leakage currents, particularly in the high-radiation environment inside the ATLAS detector, sensors are foreseen to be operated at low temperatures and to be manufactured from wafers with a high bulk resistivity of several k Omega.cm. Simulations showed the electric field inside sensors with high bulk resistivity to extend towards the sensor edge, which could lead to increased surface currents for narrow dicing edges. In order to map the electric field inside biased silicon sensors with high bulk resistivity, three diodes from ATLAS silicon strip sensor prototype wafers were studied with a monochromatic, micro-focused X-ray beam at the Diamond Light Source (Didcot, U.K.). For all devices under investigation, the electric field inside the diode was mapped and its dependence on the applied bias voltage was studied.
|
Yu, Q. X., Liang, W. H., Bayar, M., & Oset, E. (2019). Line shape and D-(*())(D)over-bar(()*()) probabilities of psi(3770) from the e(+) e(-) -> D(D)over-bar reaction. Phys. Rev. D, 99(7), 076002–17pp.
Abstract: We have performed a calculation of the D (D) over bar, D (D) over bar*, D*(D) over bar, D*(D) over bar* components in the wave function of the psi(3770). For this we make use of the P-3(0) model to find the coupling of psi(3770) to these components, that with an elaborate angular momentum algebra can be obtained with only one parameter. Then we use data for the e(+)e(-) -> D (D) over bar reaction, from where we determine a form factor needed in the theoretical framework, as well as other parameters needed to evaluate the meson-meson self-energy of the psi(3770). Once this is done we determine the Z probability to still have a vector core and the probability to have the different meson components. We find Z about 80%-85%, and the individual meson-meson components are rather small, providing new empirical information to support the largely q (q) over bar component of vector mesons, and the psi(3770) in particular. A discussion is done of the meaning of the terms obtained for the case of the open channels where the concept of probability cannot be strictly used.
|
Nath, N., Srivastava, R., & Valle, J. W. F. (2019). Testing generalized CP symmetries with precision studies at DUNE. Phys. Rev. D, 99(7), 075005–13pp.
Abstract: We examine the capabilities of the DUNE experiment in probing leptonic CP violation within the framework of theories with generalized CP symmetries characterized by the texture zeros of the corresponding CP transformation matrices. We investigate DUNE's potential to probe the two least known oscillation parameters, the atmospheric mixing angle theta(23) and the Dirac CP phase delta(CP). We fix theory-motivated benchmarks for (sin(2)theta(23), delta(CP)) and take them as true values in our simulations. Assuming 3.5 years of neutrino running plus 3.5 years in the antineutrino mode, we show that in all cases DUNE can significantly constrain and in certain cases rule out the generalized CP texture zero patterns.
|
LHCb Collaboration(Aaij, R. et al), Garcia Martin, L. M., Henry, L., Martinez-Vidal, F., Oyanguren, A., Remon Alepuz, C., et al. (2019). First Measurement of Charm Production in its Fixed-Target Configuration at the LHC. Phys. Rev. Lett., 122(13), 132002–12pp.
Abstract: The first measurement of heavy-flavor production by the LHCb experiment in its fixed-target mode is presented. The production of J/psi and D-0 mesons is studied with beams of protons of different energies colliding with gaseous targets of helium and argon with nucleon-nucleon center-of-mass energies of root s(NN) = 86.6 and 110.4 GeV, respectively. The J/psi and D-0 production cross sections in pHe collisions in the rapidity range [2, 4.6] are found to be sigma(J/psi) = 652 +/- 33(stat) +/- 42(syst) nb/nucleon and sigma(D0) = 80.8 +/- 2.4(syst) +/- 6.3(syst) μb/nucleon, where the first uncertainty is statistical and the second is systematic. No evidence for a substantial intrinsic charm content of the nucleon is observed in the large Bjorken-x region.
|
