Attempts to reproduce theoretically the width Γd⁎=80±10 MeV of the I(JP)=0(3+)d⁎(2380) dibaryon resonance established by the WASA-at-COSY Collaboration are discussed. The validity of associating the ...d⁎(2380) in quark-based models exclusively with a tightly bound ΔΔ configuration is questioned. The d⁎(2380) width and decay branching ratios into NNππ, NNπ and NN final states are studied within the Gal–Garcilazo hadronic model in which the d⁎(2380) is a πNΔ resonance embedded in the NNππ continuum some 80 MeV below the ΔΔ threshold. In particular, predictions are made for the branching ratios of the unobserved yet d⁎(2380)→NNπ decays which are suppressed in a purely-ΔΔ dibaryon model. A possible connection of the ABC effect observed in the pn→d⁎→dπ0π0 resonance reaction to the d⁎(2380) dibaryon is noted.
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What is the fastest way to heat a system which is coupled to a temperature controlled oven? The intuitive answer is to use only the hottest temperature available. However, we show that often it is ...possible to achieve an exponentially faster heating protocol. Surprisingly, this protocol can have a precooling stage-cooling the system before heating it shortens the heating time significantly. To demonstrate such improvements in many-body systems, we developed a projection-based method with which such protocols can be found in large systems, as we demonstrate on the 2D antiferromagnet Ising model.
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Five Ξ−p→ΛΛ two-body capture events in 12C and 14N emulsion nuclei, in which a pair of single-Λ hypernuclei is formed and identified by their weak decay, have been observed in (K−,K+) emulsion ...exposures at KEK and J-PARC. Applying a Ξ−-nucleus optical potential methodology to study atomic and nuclear transitions, we confirm that these capture events occur from Coulomb assisted 1pΞ− nuclear states. Long-range ΞN shell-model correlations are found essential to achieve consistency between the 12C and 14N events. The resulting Ξ-nuclear interaction is strongly attractive, with Ξ potential depth in nuclear matter VΞ≳20 MeV. Implications to multi-strangeness features of dense matter are outlined.
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Strangeness in nuclear physics Gal, A.; Hungerford, E. V.; Millener, D. J.
Reviews of modern physics,
08/2016, Volume:
88, Issue:
3
Journal Article
Peer reviewed
Open access
Extensions of nuclear physics to the strange sector are reviewed, covering data and models of Lambda and other hypernuclei, multistrange matter, and antikaon bound states and condensation. Past ...achievements are highlighted, present unresolved problems are discussed, and future directions are outlined.
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A depth of DΛ≈−28 MeV for the Λ-nucleus potential was confirmed in 1988 by studying Λ binding energies deduced from (π+,K+) spectra measured across the periodic table. Modern two-body hyperon-nucleon ...interaction models require additional interaction terms, most likely ΛNN three-body terms, to reproduce DΛ. Here we apply a suitably constructed Λ-nucleus density dependent optical potential to binding energy calculations of observed 1sΛ and 1pΛ states in the mass range 12≤A≤208. The resulting ΛNN contribution to DΛ, about 14 MeV repulsion at symmetric nuclear matter density ρ0=0.17 fm−3, makes DΛ increasingly repulsive at ρ≳3ρ0, leading possibly to little or no Λ hyperon content of neutron-star matter. This suggests in some models a stiff equation of state that may support two solar-mass neutron stars.
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Earlier work suggested that the in-medium πN threshold isovector amplitude b1(ρ) gets renormalized in pionic atoms by ∼30% away from its ρ=0 free-space value, relating such renormalization to the ...leading low-density decrease of the in-medium quark condensate <q¯q> and the pion decay constant fπ in terms of the pion-nucleon σ term σπN. Accepting the validity of this approach, we extracted σπN from a large-scale fit of pionic-atom level shift and width data across the periodic table. Our fitted value σπN=57±7 MeV is robust with respect to variation of πN interaction terms other than the isovector s-wave term with which σπN was associated. Higher order corrections to the leading order in density involve some cancellations, suggesting thereby only a few percent overall systematic uncertainty. The value of σπN derived here agrees with values obtained in several recent studies based on near-threshold πN phenomenology, but sharply disagrees with values obtained in recent direct lattice QCD calculations.
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Exotic atoms provide a unique laboratory for studying strong interactions and nuclear medium effects at zero kinetic energy. Experimental and theoretical developments of the last decade in the study ...of exotic atoms and some related low-energy reactions are reviewed. The exotic atoms considered are of
π
-
,
K
-
,
p
¯
,
Σ
-
, and also the so far unobserved
Ξ
-
atoms. The analysis of these atomic systems consists of fitting density-dependent optical potentials
V
opt
=
t
(
ρ
)
ρ
to comprehensive sets of data of strong-interaction level shifts, widths and yields across the periodic table. These provide information on the in-medium hadron–nucleon
t matrix
t
(
ρ
)
over a wide range of densities up to central nuclear densities. For pions, the review focuses on the extraction of the
π
N
in-medium
s-wave interaction from pionic atoms, which include also the deeply bound
π
-
atomic states recently observed at GSI in isotopes of Sn and Pb. Also included are recent measurements at PSI of elastic scattering of
π
±
on Si, Ca, Ni and Zr at 21.5
MeV. The experimental results are analyzed in the context of chirally motivated
π
-nuclear potentials, and the evidence for partial restoration of chiral symmetry in dense nuclear matter is critically discussed. For antikaons, we review the evidence from
K
-
atoms, and also from low-energy
K
-
p
scattering and reaction data for and against a
deep
K
¯
-nucleus potential of 150–200
MeV attraction at nuclear matter density. The case for relatively narrow deeply bound
K
-
atomic states is made, essentially independent of the potential-depth issue. Recent experimental suggestions from KEK and DA
Φ
NE (Frascati) for signals of
K
¯
-nuclear deeply bound states are reviewed, and dynamical models for calculating binding energies and widths of
K
¯
-
nuclear states are discussed. For kaons we review the evidence, from
K
+
total and reaction cross section measurements at the AGS (BNL) on Li, C, Si and Ca at
p
lab
=
500
–
700
MeV
/
c
, for significant absorptivity of
t
KN
(
ρ
)
beyond that expected from
t
KN
free
within the impulse approximation. Attempts to explain the extra absorptivity for the relatively weak interaction of
K mesons in terms of a hypothetical exotic
S
=+
1
pentaquark
Θ
+
strength are reviewed. For antiprotons the exceptionally broad data base due to the recent results of the PS209 collaboration at CERN are analyzed, together with results of radiochemical experiments. We discuss the dependence of the phenomenological
p
¯
-nucleus interaction on the model adopted for the neutron density, showing how the neutron densities favored by our comprehensive analysis are compatible with densities from other sources, including our own analysis of pionic atoms. It is also shown how the strong absorptivity of the
p
¯
-nucleus interaction, which leads to the prediction of saturation of widths in deeply bound
p
¯
-atom states, also explains the observed saturation effects in low-energy
p
¯
annihilation on nuclei. For
Σ
hyperons we review the evidence, from continuum
Σ
-
hypernuclear
(
π
-
,
K
+
)
spectra obtained recently at KEK on C, Si, Ni, In and Bi, for substantial repulsion in the
Σ
-nucleus interaction, and the relationship to the inner repulsion established earlier from the density-dependence analysis of
Σ
-
atoms and by analyses of past
(
K
-
,
π
±
)
AGS experiments.
Lastly, for
Ξ
hyperons we review prospects of measuring X-ray spectra in
Ξ
-
atoms and thereby extracting meaningful information on the
Ξ
-nucleus interaction. The significance of the latter to the physics of
Λ
Λ
hypernuclei and to extrapolation into multistrange hypernuclei are briefly reviewed.
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The Strangeness S=−2 J-PARC E07 emulsion experiment published recently two new Ξ−–14N capture events, IRRAWADDY and IBUKI, identified by observing weak-decay sequences of pairs of single-Λ ...hypernuclei and interpreted as Ξ1s− and Ξ1p− nuclear bound states, respectively, with binding energies BΞ−1s=6.27±0.27 MeV and BΞ−1p=1.27±0.21 MeV. Ξ− capture events in emulsion play a major role in determining the Ξ-nuclear and the ΛΛ potential strengths. Here we question the assignment of a Ξ1s− nuclear bound state to IRRAWADDY and offer an alternative assignment as a near-threshold Ξ1p0–14C nuclear bound state, slightly admixed with a Ξ1p−–14N nuclear bound state component corresponding to IBUKI. We also question using IBUKI's BΞ−1p value as is to determine the Ξ-nuclear potential depth. Altogether, Ξ− capture events in 12C and 16O should prove less ambiguous than in 14N.
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We investigate the light-curve properties of a sample of 26 spectroscopically confirmed hydrogen-poor superluminous supernovae (SLSNe-I) in the Palomar Transient Factory survey. These events are ...brighter than SNe Ib/c and SNe Ic-BL, on average, by about 4 and 2 mag, respectively. The peak absolute magnitudes of SLSNe-I in rest-frame g band span −22 Mg −20 mag, and these peaks are not powered by radioactive 56Ni, unless strong asymmetries are at play. The rise timescales are longer for SLSNe than for normal SNe Ib/c, by roughly 10 days, for events with similar decay times. Thus, SLSNe-I can be considered as a separate population based on photometric properties. After peak, SLSNe-I decay with a wide range of slopes, with no obvious gap between rapidly declining and slowly declining events. The latter events show more irregularities (bumps) in the light curves at all times. At late times, the SLSN-I light curves slow down and cluster around the 56Co radioactive decay rate. Powering the late-time light curves with radioactive decay would require between 1 and 10 M of Ni masses. Alternatively, a simple magnetar model can reasonably fit the majority of SLSNe-I light curves, with four exceptions, and can mimic the radioactive decay of 56Co, up to ∼400 days from explosion. The resulting spin values do not correlate with the host-galaxy metallicities. Finally, the analysis of our sample cannot strengthen the case for using SLSNe-I for cosmology.
•Overview of currently available measurement methods to separately assess E and T.•Models validated for their ability to partition between E and T are discussed briefly.•52 papers were found to ...attempt ET partitioning.•E/ET ratio was found to exceed 30% in 32 of the studies.•Despite measurement variability ∼30% of the papers show over 90% agreement for ET=E+T.
Partitioning of evapotranspiration (ET) into evaporation from the soil (E) and transpiration through the stomata of plants (T) is challenging but important in order to assess biomass production and the allocation of increasingly scarce water resources. Generally, T is the desired component with the water being used to enhance plant productivity; whereas, E is considered a source of water loss or inefficiency. The magnitude of E is expected to be quite significant in sparsely vegetated systems, particularly in dry areas or in very wet systems such as surface irrigated crops and wetlands. In these cases, ET partitioning is fundamental to accurately monitor system hydrology and to improve water management practices. This paper aims to evaluate and summarize available methods currently used to separately determine E and T components. We presuppose that, to test the accuracy of ET partitioning methods (measurements and/or modeling), all three components, i.e., E, T and ET, must be estimated independently, but recognize that sometimes one of the components is taken as the residual of the other two. Models that were validated against measurements for their ability to partition between E and T are briefly discussed. To compare approaches, 52 ET partitioning studies were considered regarding estimates of the relative amount of E and for success of agreement in closing the ET=E+T equation. The E/ET ratio was found to exceed 30% in 32 of the studies, which confirms the hypothesis that E often constitutes a large fraction of ET and deserves independent consideration. Only 20 studies estimated E and T as well as ET, and had varied results. A number of studies succeeded to estimate E+T to within 10% of measured ET. Future challenges include development of models simulating the components of ET separately and advancement of methods for continuous measurement of E, T and/or the ratio between the two.
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