排序方式: 共有46条查询结果,搜索用时 15 毫秒
21.
M. Louvel A. Genoux-Lubain G. Bizard R. Bougault R. Brou A. Buta H. Doubre D. Durand Y. El Masri H. Fugiwara K. Hagel T. Hamdani F. Hanappe S. C. Jeong G. M. Jin S. Kato J. L. Laville C. Le Brun J. F. Lecolley S. M. Lee T. Matsuse T. Motobayashi A. Pghaire J. Pter R. Regimbart F. Saint-Laurent J. C. Steckmeyer B. Tamain 《Physics letters. [Part B]》1994,320(3-4):221-226
Multifragment emission processes from highly excited nuclei produced in 40Ar + 197Au reactions at incident energies of 30 and 60 MeV/u are compared. At the lowest bombarding energy and 3.3 MeV/u excitation energy, the composite system decay process supports the hypothesis of long-lived equilibrated nucleu decaying by successive binary splittings. For excited nuclei around 5 MeV/u, the depletion observed at small relative angles in the correlation functions is interpreted as the result of a strong reduction in the fragment emission time scale. 相似文献
22.
From experimental observations of limiting temperatures in heavy ion collisions we derive the critical temperature of infinite nuclear matter Tc=16.6+/-0.86. Theoretical model correlations between Tc, the compressibility modulus K, the effective mass m*, and the saturation density rho s are then exploited to derive the quantity (K/m*)1/2 rho -1/3 s. This quantity together with calculations employing Skyrme and Gogny interactions indicates a value of K in moderately excited nuclei that is in excellent agreement with the value determined from giant monopole resonance data. 相似文献
23.
Wosnitza J Wanka S Hagel J Löhneysen H Qualls JS Brooks JS Balthes E Schlueter JA Geiser U Mohtasham J Winter RW Gard GL 《Physical review letters》2001,86(3):508-511
The quasi-two-dimensional organic superconductor beta"-(BEDT-TTF)2SF5CH2CF2SO3 (Tc approximately 4.4 K) shows very strong Shubnikov-de Haas (SdH) oscillations which are superimposed on a highly anomalous steady background magnetoresistance, Rb. Comparison with de Haas-van Alphen oscillations allows a reliable estimate of Rb which is crucial for the correct extraction of the SdH signal. At low temperatures and high magnetic fields insulating behavior evolves. The magnetoresistance data violate Kohler's rule, i.e., cannot be described within the framework of semiclassical transport theory, but converge onto a universal curve appropriate for dynamical scaling at a metal-insulator transition. 相似文献
24.
Arsene I Bearden IG Beavis D Besliu C Budick B Bøggild H Chasman C Christensen CH Christiansen P Cibor J Debbe R Enger E Gaardhøje JJ Germinario M Hagel K Hansen O Holm A Ito H Jipa A Jundt F Jørdre JI Jørgensen CE Karabowicz R Kim EJ Kozik T Larsen TM Lee JH Lee YK Lindal S Lystad G Løvhøiden G Majka Z Makeev A McBreen B Mikelsen M Murray M Natowitz J Neumann B Nielsen BS Norris J Ouerdane D Płaneta R Rami F Ristea C Ristea O Röhrich D Samset BH Sandberg D Sanders SJ Scheetz RA Staszel P 《Physical review letters》2003,91(7):072305
We present spectra of charged hadrons from Au+Au and d+Au collisions at sqrt[s(NN)]=200 GeV measured with the BRAHMS experiment at RHIC. The spectra for different collision centralities are compared to spectra from p+(-)p collisions at the same energy scaled by the number of binary collisions. The resulting ratios (nuclear modification factors) for central Au+Au collisions at eta=0 and eta=2.2 evidence a strong suppression in the high p(T) region (>2 GeV/c). In contrast, the d+Au nuclear modification factor (at eta=0) exhibits an enhancement of the high p(T) yields. These measurements indicate a high energy loss of the high p(T) particles in the medium created in the central Au+Au collisions. The lack of suppression in d+Au collisions makes it unlikely that initial state effects can explain the suppression in the central Au+Au collisions. 相似文献
25.
Absolute frequency measurements of the 2(3)S1-->2(3)P 0,1,2 atomic helium transitions around 1083 nm
Pastor PC Giusfredi G De Natale P Hagel G De Mauro C Inguscio M 《Physical review letters》2004,92(2):023001
We measure the frequency of the 2(3)S1-->2(3)P(0,1,2) transitions of helium in a metastable beam using an optical frequency comb synthesizer. The relative uncertainty of these measurements ranging from 5x10(-11) to 7x10(-12) is, to our knowledge, the most precise result for any optical helium transition. Considering existing accurate values of the 2(3)P fine structure, we measure a centroid value of the 2(3)S-2(3)P frequency of 276 736 495 624.6(2.4) kHz, improving the previous interferometric measurement by 30 times. New accurate values of the 2(3)S-2(3)P and 2(3)P Lamb-shift energies are obtained. 相似文献
26.
Arsene I Bearden IG Beavis D Besliu C Budick B Bøggild H Chasman C Christensen CH Christiansen P Cibor J Debbe R Enger E Gaardhøje JJ Germinario M Hagel K Ito H Jipa A Jundt F Jørdre JI Jørgensen CE Karabowicz R Kim EJ Kozik T Larsen TM Lee JH Lee YK Lindal S Lystad R Løvhøiden G Majka Z Makeev A Mikelsen M Murray M Natowitz J Neumann B Nielsen BS Ouerdane D Płaneta R Rami F Ristea C Ristea O Röhrich D Samset BH Sandberg D Sanders SJ Scheetz RA Staszel P Tveter TS Videbaek F Wada R Yin Z 《Physical review letters》2004,93(24):242303
We report on a study of the transverse momentum dependence of nuclear modification factors R(dAu) for charged hadrons produced in deuteron + gold collisions at sqrt[s(NN)]=200 GeV, as a function of collision centrality and of the pseudorapidity (eta=0, 1, 2.2, 3.2) of the produced hadrons. We find a significant and systematic decrease of R(dAu) with increasing rapidity. The midrapidity enhancement and the forward rapidity suppression are more pronounced in central collisions relative to peripheral collisions. These results are relevant to the study of the possible onset of gluon saturation at energies reached at BNL RHIC. 相似文献
27.
Arsene I Bearden IG Beavis D Bekele S Besliu C Budick B Bøggild H Chasman C Christensen CH Dalsgaard HH Debbe R Gaardhøje JJ Hagel K Ito H Jipa A Johnson EB Jørgensen CE Karabowicz R Katrynska N Kim EJ Larsen TM Lee JH Lindal S Løvhøiden G Majka Z Murray M Natowitz J Nielsen BS Nygaard C Płaneta R Rami F Renault F Ristea C Ristea O Röhrich D Samset BH Sanders SJ Scheetz RA Staszel P Tveter TS Videbaek F Wada R Yin Z Yang H Zgura IS 《Physical review letters》2007,98(25):252001
We present particle spectra for charged hadrons pi(+/-), K(+/-), p, and p[over] from pp collisions at square root[s] = 200 GeV measured for the first time at forward rapidities (2.95 and 3.3). The kinematics of these measurements are skewed in a way that probes the small momentum fraction in one of the protons and large fractions in the other. Large proton to pion ratios are observed at values of transverse momentum that extend up to 4 GeV/c, where protons have momenta up to 35 GeV. Next-to-leading order perturbative QCD calculations describe the production of pions and kaons well at these rapidities, but fail to account for the large proton yields and small p[over]/p ratios. 相似文献
28.
Qin L Hagel K Wada R Natowitz JB Shlomo S Bonasera A Röpke G Typel S Chen Z Huang M Wang J Zheng H Kowalski S Barbui M Rodrigues MR Schmidt K Fabris D Lunardon M Moretto S Nebbia G Pesente S Rizzi V Viesti G Cinausero M Prete G Keutgen T El Masri Y Majka Z Ma YG 《Physical review letters》2012,108(17):172701
Clustering in low density nuclear matter has been investigated using the NIMROD multidetector at Texas A&M University. Thermal coalescence modes were employed to extract densities, ρ, and temperatures, T, for evolving systems formed in collisions of 47A MeV (40)Ar+(112)Sn, (124)Sn and (64)Zn+(112)Sn, (124)Sn. The yields of d, t, (3)He, and (4)He have been determined at ρ=0.002 to 0.03 nucleons/fm(3) and T=5 to 11 MeV. The experimentally derived equilibrium constants for α particle production are compared with those predicted by a number of astrophysical equations of state. The data provide important new constraints on the model calculations. 相似文献
29.
C. Lisowski M. Knoop C. Champenois G. Hagel M. Vedel F. Vedel 《Applied physics. B, Lasers and optics》2005,81(1):5-12
Single, rf-trapped ions find various applications ranging from metrology to quantum computation. High-resolution interrogation of an extremely weak transition under best observation conditions requires an ion almost at rest. To avoid line-broadening effects such as the second-order Doppler effect or rf heating in the absence of laser cooling, excess micromotion has to be eliminated as far as possible. In this paper the motional state of a confined three-level ion is probed, taking advantage of the high sensitivity of observed dark resonances to the trapped ion’s velocity. Excess micromotion is controlled by monitoring the dark-resonance contrast with varying laser-beam geometry. The influence of different parameters such as the cooling laser intensity has been investigated experimentally and numerically. 相似文献
30.
A scheme for a terahertz frequency standard based on three-photon coherent population trapping in stored ions is proposed. Assuming the propagation directions of the three lasers obey the phase matching condition, we show that stability of few 10(-14) at 1 s can be reached with a precision limited by power broadening to 10(-11) in the less favorable case. The referenced terahertz signal can be propagated over long distances, the useful information being carried by the relative frequency of the three optical photons. 相似文献