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Journal Articles

Analysis of the ozone reduction event over the southern tip of South America in November 2009

Akiyoshi, Hideharu*; Kadowaki, Masanao; Nakamura, Haruna*; Sugita, Takafumi*; Hirooka, Toshihiko*; Harada, Yayoi*; Mizuno, Akira*

Journal of Geophysical Research; Atmospheres, 123(22), p.12523 - 12542, 2018/11

AA2018-0443.pdf:12.61MB

 Times Cited Count:1 Percentile:2.95(Meteorology & Atmospheric Sciences)

A reduction of the total ozone over the southern tip of South America lasting 3 weeks occurred in November 2009. Analyses of the ERA-Interim reanalysis data and the total ozone observed by the Ozone Monitoring Instrument indicate that the total ozone reduction event was caused by a migration of the polar vortex toward the South American continent at the time of the vortex breakup. The vortex migration is associated with an enhanced wave flux from the troposphere at 120-150$$^{circ}$$W and 50-60$$^{circ}$$S to the west of the South American continent to the stratosphere over the southern part of the continent, which led to a large negative geopotential height anomaly in the lower stratosphere. In November, a blocking event was diagnosed from the 500-hPa geopotential height over the west of the South American continent. These results suggest a relation between the long-lasting reduction of the total ozone over the southern tip of South America and the blocking phenomenon in the troposphere of the Southern Hemisphere through wave propagation from the blocking region in 2009. Analysis of the total ozone anomaly for 50-60$$^{circ}$$S and 65-75$$^{circ}$$W over the southern tip of South America in November for 1979-2015 indicates that the negative ozone anomaly in November 2009 was one of the largest anomalies in this 37-year period and was associated with the large negative geopotential height anomaly in the lower stratosphere. Analyses of dynamical fields were also conducted for other years with large geopotential height anomalies.

Journal Articles

Fast neutron detection under intense $$gamma$$-ray fields with novel nuclear emulsion technique

Ishihara, Kohei*; Takagi, Keisuke*; Minato, Haruna*; Kawarabayashi, Jun*; Tomita, Hideki*; Maeda, Shigetaka; Naka, Tatsuhiro*; Morishima, Kunihiro*; Nakano, Toshiyuki*; Nakamura, Mitsuhiro*; et al.

Radiation Measurements, 55, p.79 - 82, 2013/08

 Times Cited Count:1 Percentile:10.75(Nuclear Science & Technology)

In order to measure the neutron under a condition of high intensity of $$gamma$$-ray background, we made new nuclear emulsion based on non-sensitized OPERA emulsion which had small AgBr grain size (AgBr grain size of 60, 90 and 160 nm). The sensitivity of this new emulsion, which was a correlation between stopping power and grain density, was estimated experimentally by irradiating neutrons with several energies. We also simulated the response to $$gamma$$-ray induced electrons and compared with some experimental results by using $$^{60}$$Co $$gamma$$ source. The results showed that there might be a threshold energy deposited in one AgBr grain under which it was impossible to develop. We estimated efficiency to the $$gamma$$-ray and the neutron with this obtained response of the new emulsion.

Journal Articles

Event structure and double helicity asymmetry in jet production from polarized $$p + p$$ collisions at $$sqrt{s}$$ = 200 GeV

Adare, A.*; Afanasiev, S.*; Aidala, C.*; Ajitanand, N. N.*; Akiba, Y.*; Al-Bataineh, H.*; Alexander, J.*; Aoki, K.*; Aphecetche, L.*; Armendariz, R.*; et al.

Physical Review D, 84(1), p.012006_1 - 012006_18, 2011/07

 Times Cited Count:28 Percentile:72.42(Astronomy & Astrophysics)

We report on the event structure and double helicity asymmetry ($$A_{LL}$$) of jet production in longitudinally polarized $$p + p$$ collisions at $$sqrt{s}$$ = 200 GeV. Photons and charged particles were measured by the PHENIX experiment. Event structure was compared with the results from PYTHIA event generator. The production rate of reconstructed jets is satisfactorily reproduced with the next-to-leading-order perturbative QCD calculation. We measured $$A_{LL}$$ = -0.0014 $$pm$$ 0.0037 at the lowest $$P_T$$ bin and -0.0181 $$pm$$ 0.0282 at the highest $$P_T$$ bin. The measured $$A_{LL}$$ is compared with the predictions that assume various $$Delta G(x)$$ distributions.

Journal Articles

Identified charged hadron production in $$p + p$$ collisions at $$sqrt{s}$$ = 200 and 62.4 GeV

Adare, A.*; Afanasiev, S.*; Aidala, C.*; Ajitanand, N. N.*; Akiba, Yasuyuki*; Al-Bataineh, H.*; Alexander, J.*; Aoki, Kazuya*; Aphecetche, L.*; Armendariz, R.*; et al.

Physical Review C, 83(6), p.064903_1 - 064903_29, 2011/06

 Times Cited Count:176 Percentile:99.41(Physics, Nuclear)

Transverse momentum distributions and yields for $$pi^{pm}, K^{pm}, p$$, and $$bar{p}$$ in $$p + p$$ collisions at $$sqrt{s}$$ = 200 and 62.4 GeV at midrapidity are measured by the PHENIX experiment at the RHIC. We present the inverse slope parameter, mean transverse momentum, and yield per unit rapidity at each energy, and compare them to other measurements at different $$sqrt{s}$$ collisions. We also present the scaling properties such as $$m_T$$ and $$x_T$$ scaling and discuss the mechanism of the particle production in $$p + p$$ collisions. The measured spectra are compared to next-to-leading order perturbative QCD calculations.

Journal Articles

Azimuthal correlations of electrons from heavy-flavor decay with hadrons in $$p+p$$ and Au+Au collisions at $$sqrt{s_{NN}}$$ = 200 GeV

Adare, A.*; Afanasiev, S.*; Aidala, C.*; Ajitanand, N. N.*; Akiba, Yasuyuki*; Al-Bataineh, H.*; Alexander, J.*; Aoki, Kazuya*; Aphecetche, L.*; Aramaki, Y.*; et al.

Physical Review C, 83(4), p.044912_1 - 044912_16, 2011/04

 Times Cited Count:7 Percentile:49.81(Physics, Nuclear)

Measurements of electrons from the decay of open-heavy-flavor mesons have shown that the yields are suppressed in Au+Au collisions compared to expectations from binary-scaled $$p+p$$ collisions. Here we extend these studies to two particle correlations where one particle is an electron from the decay of a heavy flavor meson and the other is a charged hadron from either the decay of the heavy meson or from jet fragmentation. These measurements provide more detailed information about the interaction between heavy quarks and the quark-gluon matter. We find the away-side-jet shape and yield to be modified in Au+Au collisions compared to $$p+p$$ collisions.

Journal Articles

Measurement of neutral mesons in $$p$$ + $$p$$ collisions at $$sqrt{s}$$ = 200 GeV and scaling properties of hadron production

Adare, A.*; Afanasiev, S.*; Aidala, C.*; Ajitanand, N. N.*; Akiba, Y.*; Al-Bataineh, H.*; Alexander, J.*; Aoki, K.*; Aphecetche, L.*; Armendariz, R.*; et al.

Physical Review D, 83(5), p.052004_1 - 052004_26, 2011/03

 Times Cited Count:169 Percentile:98.47(Astronomy & Astrophysics)

The PHENIX experiment at RHIC has measured the invariant differential cross section for production of $$K^0_s$$, $$omega$$, $$eta'$$ and $$phi$$ mesons in $$p + p$$ collisions at $$sqrt{s}$$ = 200 GeV. The spectral shapes of all hadron transverse momentum distributions are well described by a Tsallis distribution functional form with only two parameters, $$n$$ and $$T$$, determining the high $$p_T$$ and characterizing the low $$p_T$$ regions for the spectra, respectively. The integrated invariant cross sections calculated from the fitted distributions are found to be consistent with existing measurements and with statistical model predictions.

Oral presentation

Development of automatic readout and recognition of nuclear emulsion for fast neutron measurement

Sakai, Yosuke*; Minato, Haruna*; Ishihara, Kohei*; Tomita, Hideki*; Kawarabayashi, Jun*; Iguchi, Tetsuo*; Naka, Tatsuhiro*; Asada, Takashi*; Morishima, Kunihiro*; Nakano, Toshiyuki*; et al.

no journal, , 

In order to measure a neutron-spectrum under high $$gamma$$ ray environment, a new nuclear emulsion and its data-processing method are developed. In fast neutron measurement using the nuclear emulsion which can record the three-dimensional track of a charged particle, incidence neutron energy spectrum can be obtained by analyzing the track of the recoil proton generated by the elastic scattering of a neutron. The high-speed automatic analytic method of the recoil proton track in a nuclear plate is developed. It checked that the recoil proton track length distribution obtained by viewing and automatic analysis was in agreement with a model calculation result about by the basic experiment using 14 MeV neutron.

Oral presentation

Development of automatic readout and recognition of recoiled proton track in nuclear emulsion for fast neutron measurement

Sakai, Yosuke*; Minato, Haruna*; Ishihara, Kohei*; Tomita, Hideki*; Kawarabayashi, Jun*; Iguchi, Tetsuo*; Naka, Tatsuhiro*; Asada, Takashi*; Morishima, Kunihiro*; Nakano, Toshiyuki*; et al.

no journal, , 

In order to measure a neutron-spectrum under high $$gamma$$ ray environment, a new nuclear emulsion and its data-processing method are developed. In fast neutron measurement using the nuclear emulsion which can record the three-dimensional track of a charged particle, incidence neutron energy spectrum can be obtained by analyzing the track of the recoil proton generated by the elastic scattering of a neutron. The high-speed automatic analytic method of the recoil proton track in a nuclear plate is developed. It checked that the recoil proton track length distribution obtained by viewing and automatic analysis was in agreement with a model calculation result about by the basic experiment using 14 MeV neutron.

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