912 research outputs found
High Precision Measurements of Interstellar Dispersion Measure with the upgraded GMRT
Pulsar radio emission undergoes dispersion due to the presence of free
electrons in the interstellar medium (ISM). The dispersive delay in the arrival
time of pulsar signal changes over time due to the varying ISM electron column
density along the line of sight. Correcting for this delay accurately is
crucial for the detection of nanohertz gravitational waves using Pulsar Timing
Arrays. In this work, we present in-band and inter-band DM estimates of four
pulsars observed with uGMRT over the timescale of a year using two different
template alignment methods. The DMs obtained using both these methods show only
subtle differences for PSR 1713+0747 and J19093744. A considerable offset is
seen in the DM of PSR J1939+2134 and J21450750 between the two methods. This
could be due to the presence of scattering in the former and profile evolution
in the latter. We find that both methods are useful but could have a systematic
offset between the DMs obtained. Irrespective of the template alignment methods
followed, the precision on the DMs obtained is about pc cm
using only BAND3 and pc cm after combining data from BAND3 and
BAND5 of the uGMRT. In a particular result, we have detected a DM excess of
about pc cm on 24 February 2019 for PSR J21450750.
This excess appears to be due to the interaction region created by fast solar
wind from a coronal hole and a coronal mass ejection (CME) observed from the
Sun on that epoch. A detailed analysis of this interesting event is presented.Comment: 11 pages, 6 figures, 2 tables. Accepted by A&
Measurement of the mass difference and the binding energy of the hypertriton and antihypertriton
According to the CPT theorem, which states that the combined operation of
charge conjugation, parity transformation and time reversal must be conserved,
particles and their antiparticles should have the same mass and lifetime but
opposite charge and magnetic moment. Here, we test CPT symmetry in a nucleus
containing a strange quark, more specifically in the hypertriton. This
hypernucleus is the lightest one yet discovered and consists of a proton, a
neutron, and a hyperon. With data recorded by the STAR
detector{\cite{TPC,HFT,TOF}} at the Relativistic Heavy Ion Collider, we measure
the hyperon binding energy for the hypertriton, and
find that it differs from the widely used value{\cite{B_1973}} and from
predictions{\cite{2019_weak, 1995_weak, 2002_weak, 2014_weak}}, where the
hypertriton is treated as a weakly bound system. Our results place stringent
constraints on the hyperon-nucleon interaction{\cite{Hammer2002,
STAR-antiH3L}}, and have implications for understanding neutron star interiors,
where strange matter may be present{\cite{Chatterjee2016}}. A precise
comparison of the masses of the hypertriton and the antihypertriton allows us
to test CPT symmetry in a nucleus with strangeness for the first time, and we
observe no deviation from the expected exact symmetry
Elliptic flow of electrons from heavy-flavor hadron decays in Au+Au collisions at 200, 62.4, and 39 GeV
We present measurements of elliptic flow () of electrons from the decays
of heavy-flavor hadrons () by the STAR experiment. For Au+Au collisions
at 200 GeV we report , for transverse momentum
() between 0.2 and 7 GeV/c using three methods: the event plane method
({EP}), two-particle correlations ({2}), and four-particle
correlations ({4}). For Au+Au collisions at = 62.4 and
39 GeV we report {2} for GeV/c. {2} and {4} are
non-zero at low and intermediate at 200 GeV, and {2} is consistent
with zero at low at other energies. The {2} at the two lower beam
energies is systematically lower than at 200 GeV for
GeV/c. This difference may suggest that charm quarks interact less
strongly with the surrounding nuclear matter at those two lower energies
compared to GeV.Comment: Version accepted by PR
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