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J/ψ production as a function of charged particle multiplicity in pp collisions at s =7 TeV
ALICE Collaboration,Abelev, B.,Adam, J.,Adamova, D.,Adare, A.M.,Aggarwal, M.M.,Aglieri Rinella, G.,Agocs, A.G.,Agostinelli, A.,Aguilar Salazar, S.,Ahammed, Z.,Ahmad Masoodi, A.,Ahmad, N.,Ahn, S.U.,Aki North-Holland Pub. Co 2012 Physics letters: B Vol.712 No.3
The ALICE Collaboration reports the measurement of the relative J/ψ yield as a function of charged particle pseudorapidity density dN<SUB>ch</SUB>/dη in pp collisions at s=7 TeV at the LHC. J/ψ particles are detected for p<SUB>t</SUB>>0, in the rapidity interval |y|<0.9 via decay into e<SUP>+</SUP>e<SUP>-</SUP>, and in the interval 2.5<y<4.0 via decay into μ<SUP>+</SUP>μ<SUP>-</SUP> pairs. An approximately linear increase of the J/ψ yields normalized to their event average (dN<SUB>J/ψ</SUB>/dy)/<dN<SUB>J/ψ</SUB>/dy> with (dN<SUB>ch</SUB>/dη)/<dN<SUB>ch</SUB>/dη> is observed in both rapidity ranges, where dN<SUB>ch</SUB>/dη is measured within |η|<1 and p<SUB>t</SUB>>0. In the highest multiplicity interval with <dN<SUB>ch</SUB>/dη(bin)≥24.1, corresponding to four times the minimum bias multiplicity density, an enhancement relative to the minimum bias J/ψ yield by a factor of about 5 at 2.5<y<4 (8 at |y|<0.9) is observed.
J/ψ Elliptic Flow in Pb-Pb Collisions at sNN=5.02 TeV
Acharya, S.,Adamová,, D.,Adolfsson, J.,Aggarwal, M. M.,Aglieri Rinella, G.,Agnello, M.,Agrawal, N.,Ahammed, Z.,Ahn, S. U.,Aiola, S.,Akindinov, A.,Al-Turany, M.,Alam, S. N.,Albuquerque, D. S. D. American Physical Society 2017 Physical Review Letters Vol.119 No.24
<P>We report a precise measurement of the J/psi elliptic flow in Pb-Pb collisions at root s(NN) = 5.02 TeV with the ALICE detector at the LHC. The J/psi mesons are reconstructed at midrapidity (|y| < 0.9) in the dielectron decay channel and at forward rapidity (2.5 < y < 4.0) in the dimuon channel, both down to zero transverse momentum. At forward rapidity, the elliptic flow v(2) of the J/psi is studied as a function of the transverse momentum and centrality. A positive v(2) is observed in the transverse momentum range 2<p(T)<8GeV/c in the three centrality classes studied and confirms with higher statistics our earlier results at root s(NN) = 2.76 TeV in semicentral collisions. At midrapidity, the J/psi v(2) is investigated as a function of the transverse momentum in semicentral collisions and found to be in agreement with the measurements at forward rapidity. These results are compared to transport model calculations. The comparison supports the idea that at low p(T) the elliptic flow of the J/psi originates from the thermalization of charm quarks in the deconfined medium but suggests that additional mechanisms might be missing in the models.</P>
2001년 11월 오염시기와 2002년 봄 황사시기 제주도 고산에서의 미량원소 농도 변화
한진석,김영성,문광주,안준영,김정은,류성윤,김영준,공부주,이석조 한국대기환경학회 2004 한국대기환경학회지 Vol.20 No.2
The chemical composition of PM_(2.5) was measured at Gosan. Jeju for two weeks each in November 2001 and spring 2002. In the latter part of the measurement period of November 2001, designated as the polluted period in this work, secondarily formed ion components as well as primarily emitted elemental carbon were high, PM_(2.5) mass concentration was also high in this polluted period compared with the yellow sand period, in which daily average of PM_(10) peaked up to 520㎍/㎥. Increase of major components of anthropogenic origin in the polluted period was not correlated with the variation in sea salt components while increase of crustal components in the yellow sand period was highly correlated with the variation in sea salt components. Trace elements were generally higher in the yellow sand period: however, toxic heavy metals such as zinc, cadmium and lead were the highest in the polluted period.
Measurement of an Excess in the Yield ofJ/ψat Very LowpTin Pb-Pb Collisions atsNN=2.76 TeV
Adam, J.,Adamová,, D.,Aggarwal, M. M.,Aglieri Rinella, G.,Agnello, M.,Agrawal, N.,Ahammed, Z.,Ahn, S. U.,Aiola, S.,Akindinov, A.,Alam, S. N.,Aleksandrov, D.,Alessandro, B.,Alexandre, D.,Alfaro M American Physical Society 2016 Physical review letters Vol.116 No.22
<P>We report on the first measurement of an excess in the yield of J/psi at very low transverse momentum (pT < 0.3 GeV/c) in peripheral hadronic Pb-Pb collisions at root s(NN) = 2.76 TeV, performed by ALICE at the CERN LHC. Remarkably, the measured nuclear modification factor of J/psi in the rapidity range 2.5 < y < 4 reaches about 7 (2) in the p(T) range 0-0.3 GeV/c in the 70%-90% (50%-70%) centrality class. The J/psi production cross section associated with the observed excess is obtained under the hypothesis that coherent photoproduction of J/psi is the underlying physics mechanism. If confirmed, the observation of J/psi coherent photoproduction in Pb-Pb collisions at impact parameters smaller than twice the nuclear radius opens new theoretical and experimental challenges and opportunities. In particular, coherent photoproduction accompanying hadronic collisions may provide insight into the dynamics of photoproduction and nuclear reactions, as well as become a novel probe of the quark-gluon plasma.</P>
Acharya, S.,Adamová,, D.,Adhya, S.P.,Adler, A.,Adolfsson, J.,Aggarwal, M.M.,Aglieri Rinella, G.,Agnello, M.,Agrawal, N.,Ahammed, Z.,Ahmad, S.,Ahn, S.U.,Aiola, S.,Akindinov, A.,Al-Turany, M.,Alam North-Holland Pub. Co 2019 Physics letters. Section B Vol.798 No.-
<P><B>Abstract</B></P> <P>The ALICE collaboration performed the first rapidity-differential measurement of coherent J / ψ photoproduction in ultra-peripheral Pb–Pb collisions at a center-of-mass energy <SUB> s NN </SUB> = 5.02 TeV. The J / ψ is detected via its dimuon decay in the forward rapidity region ( − 4.0 < y < − 2.5 ) for events where the hadronic activity is required to be minimal. The analysis is based on an event sample corresponding to an integrated luminosity of about 750 μb<SUP>−1</SUP>. The cross section for coherent J / ψ production is presented in six rapidity bins. The results are compared with theoretical models for coherent J / ψ photoproduction. These comparisons indicate that gluon shadowing effects play a role in the photoproduction process. The ratio of <SUP> ψ ′ </SUP> to J / ψ coherent photoproduction cross sections was measured and found to be consistent with that measured for photoproduction off protons.</P>
Acharya, S.,Adamová,, D.,Adolfsson, J.,Aggarwal, M.M.,Aglieri Rinella, G.,Agnello, M.,Agrawal, N.,Ahammed, Z.,Ahn, S.U.,Aiola, S.,Akindinov, A.,Al-Turany, M.,Alam, S.N.,Albuquerque, D.S.D.,Aleks North-Holland Pub. Co 2018 Physics letters. Section B Vol.780 No.-
<P><B>Abstract</B></P> <P>We present a measurement of azimuthal correlations between inclusive J/<I>ψ</I> and charged hadrons in p–Pb collisions recorded with the ALICE detector at the CERN LHC. The J/<I>ψ</I> are reconstructed at forward (p-going, 2.03 < y < 3.53 ) and backward (Pb-going, − 4.46 < y < − 2.96 ) rapidity via their <SUP> μ + </SUP> <SUP> μ − </SUP> decay channel, while the charged hadrons are reconstructed at mid-rapidity ( | η | < 1.8 ). The correlations are expressed in terms of associated charged-hadron yields per J/<I>ψ</I> trigger. A rapidity gap of at least 1.5 units is required between the trigger J/<I>ψ</I> and the associated charged hadrons. Possible correlations due to collective effects are assessed by subtracting the associated per-trigger yields in the low-multiplicity collisions from those in the high-multiplicity collisions. After the subtraction, we observe a strong indication of remaining symmetric structures at Δ φ ≈ 0 and Δ φ ≈ π , similar to those previously found in two-particle correlations at middle and forward rapidity. The corresponding second-order Fourier coefficient ( <SUB> v 2 </SUB> ) in the transverse momentum interval between 3 and 6 GeV/<I>c</I> is found to be positive with a significance of about 5<I>σ</I>. The obtained results are similar to the J/<I>ψ</I> <SUB> v 2 </SUB> coefficients measured in Pb–Pb collisions at <SUB> s NN </SUB> = 5.02 TeV, suggesting a common mechanism at the origin of the J/<I>ψ</I> <SUB> v 2 </SUB> .</P>
In situ 법에 의한 Cu-Nb3Sn 복합재료선재의 초전도특성과 이에 미치는 Ti의 영향 (1)
박현순,서수정,이은덕,안재민 ( H . S .Park,S . J . Suh,U . D . Lee,J . M . Ahn ) 한국열처리공학회 1993 熱處理工學會誌 Vol.6 No.1
The Cu-Nb₃Sn composites wire as a superconducting material was prepared by in situ method as follow : Cu-15wt.%Nb alloys which were melted in a high-frequency induction furnace and casted in bar were cold-worked up to the final diameter of 0.24㎜, electroplated with Sn, pre-treated in two steps and then diffused at 550∼650℃ for 24∼96hrs. The overall J_c and T_c of the specimens were measured by the four point-probe method at 10K in the magnetic field of 0 Tesla. The overall J_c of the composites wire which diffused at 550℃ after pre-treating in two steps were generally higher than those of the wire at either 600℃ or 650℃. For the specimens diffused at 550℃, the overall J_c were increased until 72hrs. of diffusion time and then decreased. However, in case of diffusion at 600℃ and 650℃, the overall J_c were gradually decreased from the beginning. The maximum overall J_c obtained in this experiment was 1.3×10⁴A/㎠, which was measured for the specimen diffused at 550 for 72hrs. When the specimens were diffused at 550℃, for 72hrs. after pre-treating, the measured critical temperature, T_c was 16.19K. Similar T_c value were obtained in other specimens regardless of diffusion time and temperature.