The refractive indices
n
(ω) and absorption coefficients α(ω) of the jawbone and the human bone substitute Cerabone® were determined in vitro by the terahertz (THz) time-domain spectroscopy (TDS) in ...a wide frequency range from 0.2 to 2.5 THz. It is shown that the refractive index of the human jawbone changes between the values of 2.075 and 2.157, and of the Cerabone® between 2.4 and 2.65. The absorption coefficient of the human jawbone increases depending on the frequency from 1.7 cm
–1
to 178.5 cm
–1
, showing several resonance absorption lines at the values greater than 1.6 THz. The absorption coefficient of Cerabone® increases from zero to 80 cm
–1
, and the resonance absorption occurs at 1.7 THz. The obtained results allow us to determine the proximity of the physical properties of the bone transplantation material Cerabone® with the natural bone matrix.
Terahertz time-domain spectroscopy (THz-TDS) was applied to study properties of a human jawbone in transmission geometry. The fiber femtosecond laser (Fx-100, IMRA) with a pulse width of 113 fs, a ...central wavelength of 800 nm and an average power of 120 mW was used as a laser source for pumping and detecting terahertz pulses. The refractive indices n(ω) and absorption coefficients α(ω) of the human jawbone and bone substitute Cerabone® were determined in vitro by the THz-TDS in a wide frequency range from 0.2 to 2.5 THz. It is shown that the refractive index of the human jawbone changes between the values of 2.24 and 2.36, and Cerabone® between 2.4 and 2.65. The absorption coefficient of the human jawbone depending on frequency increases from 1.7 cm−1 to 178.5 cm −1, showing several resonance absorption lines after 1.6 THz. The absorption coefficient of Cerabone® increases from zero to 80 cm−1, and the resonance absorption occurs at 1.7 THz. The experimental results indicate that n(f) and α(f) of a human jawbone change with the alteration of the direction of the linear polarization vector of the electric field of THz pulse relative to the axis of the plate of the human jawbone. The obtained results allowed us to determine the proximity of the physical properties of the Cerabone® with the natural bone matrix.
At sufficiently high temperature and energy density, nuclear matter undergoes a transition to a phase in which quarks and gluons are not confined: the quark-gluon plasma (QGP). Such an exotic state ...of strongly interacting quantum chromodynamics matter is produced in the laboratory in heavy nuclei high-energy collisions, where an enhanced production of strange hadrons is observed. Strangeness enhancement, originally proposed as a signature of QGP formation in nuclear collisions, is more pronounced for multi-strange baryons. Several effects typical of heavy-ion phenomenology have been observed in high-multiplicity proton-proton (pp) collisions, but the enhanced production of multi-strange particles has not been reported so far. Here we present the first observation of strangeness enhancement in high-multiplicity proton-proton collisions. We find that the integrated yields of strange and multi-strange particles, relative to pions, increases significantly with the event charged-particle multiplicity. The measurements are in remarkable agreement with the p-Pb collision results, indicating that the phenomenon is related to the final system created in the collision. In high-multiplicity events strangeness production reaches values similar to those observed in Pb-Pb collisions, where a QGP is formed.
A
bstract
We report the measured transverse momentum (
p
T
) spectra of primary charged particles from pp, p-Pb and Pb-Pb collisions at a center-of-mass energy
s
N
N
=
5.02
TeV in the kinematic range ...of 0
.
15
< p
T
<
50 GeV/
c
and |
η
|
<
0
.
8. A significant improvement of systematic uncertainties motivated the reanalysis of data in pp and Pb-Pb collisions at
s
N
N
=
2.76
TeV, as well as in p-Pb collisions at
s
N
N
=
5.02
TeV, which is also presented. Spectra from Pb-Pb collisions are presented in nine centrality intervals and are compared to a reference spectrum from pp collisions scaled by the number of binary nucleon-nucleon collisions. For central collisions, the
p
T
spectra are suppressed by more than a factor of 7 around 6–7 GeV/
c
with a significant reduction in suppression towards higher momenta up to 30 GeV/
c
. The nuclear modification factor
R
pPb
, constructed from the pp and p-Pb spectra measured at the same collision energy, is consistent with unity above 8 GeV/
c
. While the spectra in both pp and Pb-Pb collisions are substantially harder at
s
N
N
=
5.02
TeV compared to 2.76 TeV, the nuclear modification factors show no significant collision energy dependence. The obtained results should provide further constraints on the parton energy loss calculations to determine the transport properties of the hot and dense QCD matter.
This work presents new constraints on the existence and the binding energy of a possible Λ–Λ bound state, the H-dibaryon, derived from Λ–Λ femtoscopic measurements by the ALICE collaboration. The ...results are obtained from a new measurement using the femtoscopy technique in ▪ collisions at s=13 TeV and p–Pb collisions at sNN=5.02 TeV, combined with previously published results from ▪ collisions at s=7 TeV. The Λ–Λ scattering parameter space, spanned by the inverse scattering length f0−1 and the effective range d0, is constrained by comparing the measured Λ–Λ correlation function with calculations obtained within the Lednický model. The data are compatible with hypernuclei results and lattice computations, both predicting a shallow attractive interaction, and permit to test different theoretical approaches describing the Λ–Λ interaction. The region in the (f0−1,d0) plane which would accommodate a Λ–Λ bound state is substantially restricted compared to previous studies. The binding energy of the possible Λ–Λ bound state is estimated within an effective-range expansion approach and is found to be BΛΛ=3.2−2.4+1.6(stat)−1.0+1.8(syst) MeV.
Direct photon production at mid-rapidity in Pb–Pb collisions at sNN=2.76 TeV was studied in the transverse momentum range 0.9<pT<14 GeV/c. Photons were detected with the highly segmented ...electromagnetic calorimeter PHOS and via conversions in the ALICE detector material with the e+e− pair reconstructed in the central tracking system. The results of the two methods were combined and direct photon spectra were measured for the 0–20%, 20–40%, and 40–80% centrality classes. For all three classes, agreement was found with perturbative QCD calculations for pT≳5 GeV/c. Direct photon spectra down to pT≈1 GeV/c could be extracted for the 20–40% and 0–20% centrality classes. The significance of the direct photon signal for 0.9<pT<2.1 GeV/c is 2.6σ for the 0–20% class. The spectrum in this pT range and centrality class can be described by an exponential with an inverse slope parameter of (297±12stat±41syst) MeV. State-of-the-art models for photon production in heavy-ion collisions agree with the data within uncertainties.
This Letter presents the first experimental observation of the attractive strong interaction between a proton and a multistrange baryon (hyperon) Ξ−. The result is extracted from two-particle ...correlations of combined p−Ξ−⊕p¯−Ξ¯+ pairs measured in p−Pb collisions at sNN=5.02 TeV at the LHC with ALICE. The measured correlation function is compared with the prediction obtained assuming only an attractive Coulomb interaction and a standard deviation in the range 3.6, 5.3 is found. Since the measured p−Ξ−⊕p¯−Ξ¯+ correlation is significantly enhanced with respect to the Coulomb prediction, the presence of an additional, strong, attractive interaction is evident. The data are compatible with recent lattice calculations by the HAL-QCD Collaboration, with a standard deviation in the range 1.8, 3.7. The lattice potential predicts a shallow repulsive Ξ− interaction within pure neutron matter and this implies stiffer equations of state for neutron-rich matter including hyperons. Implications of the strong interaction for the modeling of neutron stars are discussed.
Invariant differential yields of deuterons and antideuterons in pp collisions at s = 0.9, 2.76 and 7 TeV and the yields of tritons, He3 nuclei, and their antinuclei at s = 7 TeV have been measured ...with the ALICE detector at the CERN Large Hadron Collider. The measurements cover a wide transverse momentum (pT) range in the rapidity interval |y|
The azimuthal anisotropy coefficient v2 of prompt D0, D+, D∗+, and Ds+ mesons was measured in midcentral (30%-50% centrality class) Pb-Pb collisions at a center-of-mass energy per nucleon pair ...sNN=5.02 TeV, with the ALICE detector at the LHC. The D mesons were reconstructed via their hadronic decays at midrapidity, |y|
The first measurements of anisotropic flow coefficients vn for mid-rapidity charged particles in Xe–Xe collisions at sNN=5.44 TeV are presented. Comparing these measurements to those from Pb–Pb ...collisions at sNN=5.02 TeV, v2 is found to be suppressed for mid-central collisions at the same centrality, and enhanced for central collisions. The values of v3 are generally larger in Xe–Xe than in Pb–Pb at a given centrality. These observations are consistent with expectations from hydrodynamic predictions. When both v2 and v3 are divided by their corresponding eccentricities for a variety of initial state models, they generally scale with transverse density when comparing Xe–Xe and Pb–Pb, with some deviations observed in central Xe–Xe and Pb–Pb collisions. These results assist in placing strong constraints on both the initial state geometry and medium response for relativistic heavy-ion collisions.
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