The azimuthal correlation,
Δ
ϕ
12
, of high transverse momentum jets in pp collisions at
s
=
13
TeV is studied by applying PB-TMD distributions to NLO calculations via MCatNLO together with the ...PB-TMD parton shower. A very good description of the cross section as a function of
Δ
ϕ
12
is observed. In the back-to-back region of
Δ
ϕ
12
→
π
, a very good agreement is observed with the PB-TMD Set 2 distributions while significant deviations are obtained with the PB-TMD Set 1 distributions. Set 1 uses the evolution scale while Set 2 uses transverse momentum as an argument in
α
s
, and the above observation therefore confirms the importance of an appropriate soft-gluon coupling in angular ordered parton evolution. The total uncertainties of the predictions are dominated by the scale uncertainties of the matrix element, while the uncertainties coming from the PB-TMDs and the corresponding PB-TMD shower are very small. The
Δ
ϕ
12
measurements are also compared with predictions using MCatNLO together
Pythia
8, illustrating the importance of details of the parton shower evolution.
Full text
Available for:
DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
The polarization of $Λ$ and $\bar{Λ}$ hyperons along the beam direction has been measured relative to the second and third harmonic event planes in isobar Ru + Ru and Zr + Zr collisions at ...$\sqrt{^SNN}$ = 200 GeV. This is the first experimental evidence of the hyperon polarization by the triangular flow originating from the initial density fluctuations. The amplitudes of the sine modulation for the second and third harmonic results are comparable in magnitude, increase from central to peripheral collisions, and show a mild pT dependence. The azimuthal angle dependence of the polarization follows the vorticity pattern expected due to elliptic and triangular anisotropic flow, and qualitatively disagree with most hydrodynamic model calculations based on thermal vorticity and shear induced contributions. The model results based on one of existing implementations of the shear contribution lead to a correct azimuthal angle dependence, but predict centrality and pT dependence that still disagree with experimental measurements. Thus, our results provide stringent constraints on the thermal vorticity and shear-induced contributions to hyperon polarization. Finally, comparison to previous measurements at RHIC and the LHC for the second-order harmonic results shows little dependence on the collision system size and collision energy.
Full text
Available for:
CMK, CTK, FMFMET, IJS, NUK, PNG, UL, UM
The deconfined quark-gluon plasma (QGP) created in relativistic heavy-ion collisions enables the exploration of the fundamental properties of matter under extreme conditions. Noncentral collisions ...can produce strong magnetic fields on the order of 1018 G, which offers a probe into the electrical conductivity of the QGP. In particular, quarks and antiquarks carry opposite charges and receive contrary electromagnetic forces that alter their momenta. This phenomenon can be manifested in the collective motion of final-state particles, specifically in the rapidity-odd directed flow, denoted as v1(y). Here, we present the charge-dependent measurements of dv1/dy near midrapidities for π±, K±, and $p(\bar{p})$ in Au+Au and isobar $(^{96}_{44}Ru+^{96}_{44}Ru$ and $^{96}_{40}Zr+^{96}_{40}Zr)$ collisions at $\sqrt{s_{NN}}=200$ GeV, and in Au+Au collisions at 27 GeV, recorded by the STAR detector at the Relativistic Heavy Ion Collider. The combined dependence of the v1 signal on collision system, particle species, and collision centrality can be qualitatively and semi-quantitatively understood as several effects on constituent quarks. While the results in central events can be explained by the u and d quarks transported from initial-state nuclei, those in peripheral events reveal the impacts of the electromagnetic field on the QGP. Our data put valuable constraints on the electrical conductivity of the QGP in theoretical calculations.
Full text
Available for:
CMK, CTK, FMFMET, IJS, NUK, PNG, UL, UM, UPUK
We report the triton (t) production in midrapidity (|y|<0.5) Au+Au collisions at sqrts_{NN}=7.7-200 GeV measured by the STAR experiment from the first phase of the beam energy scan at the ...Relativistic Heavy Ion Collider. The nuclear compound yield ratio (N_{t}×N_{p}/N_{d}^{2}), which is predicted to be sensitive to the fluctuation of local neutron density, is observed to decrease monotonically with increasing charged-particle multiplicity (dN_{ch}/dη) and follows a scaling behavior. The dN_{ch}/dη dependence of the yield ratio is compared to calculations from coalescence and thermal models. Enhancements in the yield ratios relative to the coalescence baseline are observed in the 0%-10% most central collisions at 19.6 and 27 GeV, with a significance of 2.3σ and 3.4σ, respectively, giving a combined significance of 4.1σ. The enhancements are not observed in peripheral collisions or model calculations without critical fluctuation, and decreases with a smaller p_{T} acceptance. The physics implications of these results on the QCD phase structure and the production mechanism of light nuclei in heavy-ion collisions are discussed.
Full text
Available for:
CMK, CTK, FMFMET, IJS, NUK, PNG, UL, UM
Aim: This research was designed to evaluate the anti-inflammatory and analgesic activities of Parinari curatellifolia methanol leaf extract in albino rats.
Methodology: Phytochemical screening was ...carried out using standard methods. Anti-inflammatory activity of the extract was done using egg albumin and formalin induced hind paw edema model. Analgesic effect was evaluated using hot plate induced pain and acetic acid induced writhing test. For each model twenty (20) rats were used, divided into five (5) groups of four (4) rats each.
Results: Parinari curatellifolia revealed the presence of alkaloids, flavonoids, tannins and phenols while steroids, anthraquinone, terpenoids and glycoside were not detected. For the egg albumin induced inflammation, the group treated with the standard drug (indomethacin) and the group that received the highest dose of the extract were significantly lower (P<0.05) than all the other groups with percentage inhibitions at 25.56% and 24.44% respectively there was no significant difference (P>0.05). For the formalin induced anti-inflammatory activity, at the 1st hour, the normal control group had its paw volume significantly different (P<0.05) from the treated groups. This trend was observed at the 2nd, 3rd and 4th hour. The hot plate method results revealed significant increased (P<0.05) in the analgesic activity of PCMLE at 400mg/kg body weight and the drug treated group when the control was compared with the treated groups with percentage inhibition of 34.32% and 52.94% respectively. The acetic acid induced writhing test revealed that the extract at the three doses of 100, 200 and 400 mg/kg body weight, showed a significant (P<0.05) percentage inhibition of 32.31%, 36.92% and 47.69%, respectively compared to negative control.
Conclusion: This justifies the use of Parinari curatellifolia locally in the management of pain and inflammation.
In relativistic heavy-ion collisions, a global spin polarization, PH, of Λ and Λ¯¯ hyperons along the direction of the system angular momentum was discovered and measured across a broad range of ...collision energies and demonstrated a trend of increasing PH with decreasing $\sqrt{s{NN}}$. A splitting between Λ and Λ¯¯ polarization may be possible due to their different magnetic moments in a late-stage magnetic field sustained by the quark-gluon plasma which is formed in the collision. The results presented in this study find no significant splitting at the collision energies of $\sqrt{s{NN}}$ = 19.6 and 27 GeV in the BNL Relativistic Heavy Ion Collisions Beam Energy Scan Phase II using the STAR detector, with an upper limit of PΛ¯¯ – PΛ < 0.24 % and PΛ¯¯ – PΛ < 0.35 %, respectively, at a 95% confidence level. We derive an upper limit on the naive extraction of the late-stage magnetic field of B < 9.4 × 1012 T and B < 1.4 × 1013 T at $\sqrt{s{NN}}$ = 19.6 and 27 GeV, respectively, although more thorough derivations are needed. Differential measurements of PH were performed with respect to collision centrality, transverse momentum, and rapidity. With our current acceptance of |y| < 1 and uncertainties, we observe no dependence on transverse momentum and rapidity in this analysis. These results challenge multiple existing model calculations following a variety of different assumptions which have each predicted a strong dependence on rapidity in this collision-energy range.
Full text
Available for:
CMK, CTK, FMFMET, IJS, NUK, PNG, UM
The chiral magnetic effect (CME) is a phenomenon that arises from the QCD anomaly in the presence of an external magnetic field. The experimental search for its evidence has been one of the key goals ...of the physics program of the Relativistic Heavy-Ion Collider. The STAR Collaboration has previously presented the results of a blind analysis of isobar collisions ( Ru 44 96 + Ru 44 96 , Zr 40 96 + Zr 40 96 ) in the search for the CME. The isobar ratio ( Y ) of CME-sensitive observable, charge separation scaled by elliptic anisotropy, is close to but systematically larger than the inverse multiplicity ratio, the naive background baseline. This indicates the potential existence of a CME signal and the presence of remaining nonflow background due to two- and three-particle correlations, which are different between the isobars. In this postblind analysis, we estimate the contributions from those nonflow correlations as a background baseline to Y , utilizing the isobar data as well as Heavy Ion Jet Interaction Generator simulations. This baseline is found consistent with the isobar ratio measurement, and an upper limit of 10% at 95% confidence level is extracted for the CME fraction in the charge separation measurement in isobar collisions at s NN = 200 GeV. Published by the American Physical Society 2024
Full text
Available for:
CMK, CTK, FMFMET, IJS, NUK, PNG, UL, UM, UPUK
Density fluctuations near the QCD critical point can be probed via an intermittency analysis in relativistic heavy-ion collisions. We report the first measurement of intermittency in Au+Au collisions ...at sNN = 7.7-200 GeV measured by the STAR experiment at the Relativistic Heavy Ion Collider (RHIC). The scaled factorial moments of identified charged hadrons are analyzed at mid-rapidity and within the transverse momentum phase space. We observe a power-law behavior of scaled factorial moments in Au+Au collisions and a decrease in the extracted scaling exponent (ν) from peripheral to central collisions. The ν is consistent with a constant for different collisions energies in the mid-central (10-40%) collisions. Moreover, the ν in the 0-5% most central Au+Au collisions exhibits a non-monotonic energy dependence that reaches a minimum around sNN = 27 GeV. The physics implications on the QCD phase structure are discussed.
Full text
Available for:
GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
We report systematic measurements of dielectron (e+e–) invariant-mass Mee spectra at midrapidity in Au + Au collisions at sNN=27 = 27, 39, and 62.4 GeV taken with the STAR detector at the ...Relativistic Heavy Ion Collider. For all energies studied, a significant excess yield of dielectrons is observed in the low-mass region ( 0.40 < Mee < 0.75 MeV / c2) compared to hadronic cocktail simulations at freeze-out. Models that include an in-medium broadening of the ρ -meson spectral function consistently describe the observed excess. In addition, we report acceptance-corrected dielectron-excess spectra for Au + Au collisions at midrapidity ( |yee| < 1) in the 0–80% centrality bin for each collision energy. The integrated excess yields for 0.4 < Mee < 0.75 GeV / c2, normalized by the charged particle multiplicity at midrapidity, are compared with previously published measurements for Au + Au at sNN=27 = 19.6 and 200 GeV. Models that include an in-medium broadening of the ρ -meson spectral function consistently describe the observed excess. Furthermore, the normalized excess yields in the low-mass region show no significant collision energy dependence. The data, however, are consistent with model calculations that demonstrate a modest energy dependence.
Full text
Available for:
CMK, CTK, FMFMET, IJS, NUK, PNG, UM
PDF
