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          D*-Meson Photoproduction off the Proton Target with the Regge Contribution

          남승일 한국물리학회 2020 New Physics: Sae Mulli Vol.70 No.1

          We investigate the four individual photoproduction channels off the proton target, corresponding to the isospin single and triplet charmed baryons, p ! D 0+c and p ! (D +0c ;D 0+c ;D ++ c ). In this work, we estimate the unpolarized total cross sections as guidance for possible future J-PARC experiments. For this purpose, we employ the effective Lagrangian approach at the tree-level Born approximation with the t-channel D and D meson Reggized propagators. In addition, phenomenological form factors are taken into account for considering the spatial extension of the hadrons involved. From the numerical calculations, we observed that cross sections of tens of nanobarns for +c production and a few nanobarns for the ++ c ones, which are in the detectable range of cross sections in presently available high-energy experiments.

        • KCI등재

          인스탄톤 모형을 이용한 $N_f=2$ 양자색소역학 위상구조 연구

          남승일 한국물리학회 2017 New Physics: Sae Mulli Vol.67 No.3

          In this work, we investigate the phase diagram of quantum chromodynamics (QCD) for $N_f=2$ as a function of the temperature and the density by employing the liquid-instanton model. For this purpose, we take into account two cases, one with zero and one with finite current-quark masses. The instanton parameters, such as the average (anti)instanton size $\bar{\rho}$ and the inter-(anti)instanton distance $\bar{R}$, are given as functions of the temperature $T$ via the trivial-holonomy caloron solution. From the numerical calculations, we confirm that the phase-transition patterns follow the appropriate universal class, $i.e.$, the second-order phase transition for the massless quarks and the crossover for the finite-mass quarks. The critical-end point (CEP) are found to be (187,92) MeV and (232,72) MeV for the massless and the finite-mass quarks. Our results are compared with other theoretical results from the Nambu—Jona-Lasinio model (NJL). 본 연구에서는 인스탄톤 진공을 이용한 유효 모형인 액체-인스탄톤 모형 (liquid-instanton model, LIM)을 이용하여 $N_f=2$ 에서의 양자색소역학적 위상구조를 온도($T$)와 쿼크 화학 포텐셜($\mu$)의 함수로서 연구하고자 한다. 이를 위해 쿼크의 전류 질량(current-quark mass, $m$)이 0인 경우와 유한한 경우 $m_q$ = 5 MeV를 고려한다. 인스탄톤의 평균 크기($\bar{\rho}$), 인스탄톤간 평균 거리($\bar{R}$) 등의 모형 매개변수들은 자명한 홀로노미의 칼로론해(trivial-caloron solution)를 이용하여 계산되었다. 수치계산으로부터 쿼크 전류 질량에 의한 정확한 상전이(phase transition) 패턴이 확인되었으며, 상전이의 변화가 일어나는 임계 종말점(critical-end point, CEP)은 쿼크 전류 질량 $m$ = (0,5) MeV에 대해 각각 (187,92) MeV과 (232,72) MeV로 주어진다. 또한 본 이론 계산 결과를 다른 유효 모형인 남부-요나-라시니오(Nambu-Jona-Lasinio, NJL)모형의 결과와 비교하였다.

        • KCI등재

          QCD Topological Susceptibility from the Nonlocal Chiral Quark Model

          남승일,Chung-Wen Kao 한국물리학회 2017 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.70 No.12

          We investigate the quantum chromodynamics (QCD) topological susceptibility by using the semi-bosonized nonlocal chiral-quark model (SB-NLQM) for the leading large-Nc contributions. This model is based on the liquid-instanton QCD-vacuum configuration, in which SU(3) flavor symmetry is explicitly broken by the finite current-quark mass (mu,d,ms) (5, 135) MeV. To compute , we derive the local topological charge-density operator Qt(x) from the effective action of SB-NLQM. We verify that the derived expression for in our model satisfies the Witten- Veneziano (WV) and the Leutwyler-Smilga (LS) formulae, and the Crewther theorem in the chiral limit by construction. Once the average instanton size and the inter-instanton distance are fixed with ¯ = 1/3 fm and ¯R = 1 fm, respectively, all the other parameters are determined self-consistently within the model. We obtain = (167.67MeV)4, which is comparable with the empirical value = (175±5MeV)4 whereas it turns out that QL = (194.30MeV)4 in the quenched limit. Thus, we conclude that the value of will be reduced around 10 20% by the dynamical-quark contribution.

        • KCI등재

          Pion Electromagnetic Form Factor and ρ-meson Mass Shift at Finite Density

          남승일,김현철 한국물리학회 2011 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.59 No.2

          We investigate the pion electromagnetic form factor and the mass dropping of the ρ meson at finite density. We first calculate the pion electromagnetic form factor and the corresponding charge radii within the framework of the nonlocal chiral quark model from the instanton vacuum both at zero and finite densities. In order to relate the change in the pion charge radius to that of the ρ-meson mass at finite density, we employ the vector-meson dominance for the pion electromagnetic form factor. The pion charge radius turns out to get larger as the quark chemical potential increases. As a result, the ρ-meson mass falls off as the quark chemical potential grows and is found to drop by about 10% at normal nuclear matter density: m_ρ^*/m_ρ ≒ 1 − 0.12 μ_B/μ_0, which is compatible to the results of the measurement at the KEK recently.

        • KCI등재

          Regularization Dependence of the S = 0 and the S = - 1 Meson-BaryonSystem in the Chiral Unitary Model

          남승일,Hyun-Chul Kim,Atsushi Hosaka,Daisuke Jido,Tetsuo Hyodo 한국물리학회 2004 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.45 No.3

          We investigate the dependences of the s-wave meson-baryon scattering amplitudes on dierent regularizations within the framework of the chiral unitary model. We employ two dierent regularization schemes, i.e., dimensional and form-factor regularizations, to tame the divergences in the model. We also use those regularization schemes to study the analytic structures of the T-matrices. We nd that while the form-factor regularizaion produces almost the same results as the dimensional regularization does, the on-shell approximation is to some extent limited in the case of the form-factor regularization. Having chosen parameters properly, we show that the regularization dependences can be minimized.

        • 대한해협 대륙붕 해역의 홀로세 해수면 상승과 고환경변화

          남승일,장정해,공기수,김성필,유동근 한국제4기학회 2003 제사기학회지 Vol.17 No.1

          대한해협 북서연안의 내대륙붕(약 40m수심)에서 약 31m의 심부 코아 SSDP-102를 시추하여, 고해상의 층서를 확립하고 홀로세 해침에 의한 고환경 변화를 복원하기 위하여 퇴적상과 유기지화학 분석을 수행하였다. 시추 코아의 층서는 6점의 AMS $^{14}C$ 연대측정 자료를 이용하였으며, 약 12.1 ka BP 이후의 퇴적환경 변화가 기록되어 있다. 탄성파 탐사자료와 퇴적물 암상 그리고 유기지화학 자료에 의하면 코아 SSDP-102는 음향 기반암 위에 쌓인 3개의 퇴적 단위 (Unit III, II, I)로 나뉘어 지며, 각 Uni에는 해침이 시작된 이후 3회에 걸쳐 뚜렷한 퇴적환경변화가 기록되어 있다. (1) Unit III은 12.1에서 6.2 ka BP까지 해침이 시작된 염하구 환경: (2) Unit II는 6.2에서 5.1 ka BP까지 해수면 상승이 둔화된 연안환경: (3) Unit 1은 5.1 ka BP 이후 현재까지 연안 및 외해 환경에서 퇴적되었다. 특히 대마난류의 영향을 받는 현재의 퇴적환경은 약 5.1 ka BP 이후 점진적으로 형성된 것으로 보인다. A 31m-long sediment core (SSDP-102) was taken from the inner shelf (about 40m water-depth) off the northwestern coast of the Korea Strait. Detailed lithofacies and organic-geochemical analyses were performed to establish a high-resolution stratigraphy in the Korea Strait shelf and to reconstruct the paleoenvironmental changes associated with the Holocene marine transgression. The stratigraphic framework of the core was primarily established using 6 AMS $^{14}C$ ages. The sedimentary record of the core SSDP-102 allows for the reconstruction of the paleoenvironmental changes during the last 12.1 ka BP. According to the high-resolution seismic reflection profiles, lithofacies and organic-geochemical data, the core SSDP-102 can be divided into three units (III to I in ascending order) above the acoustic basement. The three units reflect distinct changes of depositional environments resulted from the post-glacial marine transgression. Therefore, it is suggested that three phases of sea-level change have occurred within the inner shelf of the Korea Strait following the Holocene marine transgression. (1) estuarine environments from ca. 12.1 to 6.2 ka BP; (2) near-shore environments with a period of decreased rising of sea level between 6.2 and 5.1 ka BP; (3) near-shore to modem marine environments after 5.1 ka BP. In particular, the present marine conditions influenced by the warm Tsushima Current have been gradually established after ca. 5.1 ka BP.

        • KCI등재

          비섭동 영역에서의 제트-담금질 매개변수 $\hat{q}$

          남승일 한국물리학회 2016 New Physics: Sae Mulli Vol.66 No.6

          We investigate the jet-quenching parameter $\hat{q}$ for the quark-gluon plasma (QGP) for $N_c=3$, defined nonperturbatively with the Wilson loop in the light-cone (LC) coordinate, at finite temperature $(T)$. Considering the effective static (heavy) quark-antiquark potential $V_{\bar{Q}Q}=\sigma L+C-A/L$, where $L$ indicates the LC transverse separation between the quarks, we obtain $\hat{q}\approx8V_{\bar{Q}Q}/L^2$. The $T$ dependences for $L$ and other relevant parameters are extracted from the $T$-dependent instanton (trivial-holonomy caloron) length parameters and the lattice quantum chromodynamics (QCD) data. By choosing $L\approx{a}\approx\bar{\rho}_T$, in which $a$ and $\bar{\rho}_T$ denote the lattice spacing and the $T$-dependent average (anti)instanton size, respectively, we find numerically that $\hat{q}=(5\sim25)\,\mathrm{GeV/fm}$ for $T= 0\sim 0.6$ GeV, these values are consistent with other estimates from AdS/CFT and experimental analyses. $\hat{q}$ is produced almost completely by the Coulomb and constant potentials of $V_{\bar{Q}Q}$. We also observe that the ratio $T^3/\hat{q}$ saturates at $\sim4.45\times10^{-2}$ for $T ≳ 0.4$ GeV, indicating a strongly-coupled QGP, and that $\hat{q}$ is proportional to $T^3$ for high $T$. 본 연구는 유한온도 쿼크-글루온 플라즈마에서 중요한 역할을 하는 비섭동 영역에서의 제트-담금질 매개변수($\hat{q}$)를 $N_c=3$의 경우에 대하여, 광원추상의 윌슨 루프를 이용하여 연구하였다. 무거운 쿼크간 광원추상에서 거리가 $L$ 일때, 유효 포텐셜이 $V_{\bar{Q}Q}=\sigma L+C-A/L$로 주어지는 것을 고려하면, $\hat{q}\approx8V_{\bar{Q}Q}/L^2$이 됨을 보인다. $L$과 다른 모형 변수들의 온도 의존성은 자명한 홀로노미(trivial-holonomy)를 가진 칼로론(caloron)과 격자 QCD로부터 결정되어진다. $a$ and $\bar{\rho}_T$를 각각 격자 QCD 간격과 온도에 의존하는 평균적인 인스탄톤의 크기라 하고, 차원 분석을 통해 $L\approx{a}\approx\bar{\rho}_T$를 가정하면, $T=(0\sim0.6)$에서 $\hat{q}=(5\sim25)\,\mathrm{GeV/fm}$로 주어진다. 이 값 은 AdS/CFT 및 실험 분석에서의 다른 추정과 잘 일치한다. 수치결과의 분석을 통해, 포텐셜 $V_{\bar{Q}Q}$중 쿨롱 및 상수 부분의 기여가 가장 중요함을 알 수 있었다. 또한 $T\gtrsim0.4$ GeV의 영역에서 비율 $T^3/\hat{q}$는 약 $4.45\times10^{-2}$에 근접하며, 이는 $\hat{q}$ 가 높은 온도에서 $T^3$의 형태로 거동함을 보여준다.

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