106 research outputs found
HIV Testing and Care in Canadian Aboriginal Youth: A community based mixed methods study
<p>Abstract</p> <p>Background</p> <p>HIV infection is a serious concern in the Canadian Aboriginal population, particularly among youth; however, there is limited attention to this issue in research literature. The purpose of this national study was to explore HIV testing and care decisions of Canadian Aboriginal youth.</p> <p>Methods</p> <p>A community-based mixed-method design incorporating the Aboriginal research principles of Ownership, Control, Access and Possession (OCAP) was used. Data were collected through surveys (n = 413) and qualitative interviews (n = 28). Eleven community-based organizations including urban Aboriginal AIDS service organizations and health and friendship centres in seven provinces and one territory assisted with the recruitment of youth (15 to 30 years).</p> <p>Results</p> <p>Average age of survey participants was 21.5 years (median = 21.0 years) and qualitative interview participants was 24.4 years (median = 24.0). Fifty-one percent of the survey respondents (210 of 413 youth) and 25 of 28 interview participants had been tested for HIV. The most common reason to seek testing was having sex without a condom (43.6%) or pregnancy (35.4%) while common reasons for not testing were the perception of being low HIV risk (45.3%) or not having had sex with an infected person (34.5%). Among interviewees, a contributing reason for not testing was feeling invulnerable. Most surveyed youth tested in the community in which they lived (86.5%) and 34.1% visited a physician for the test. The majority of surveyed youth (60.0%) had tested once or twice in the previous 2 years, however, about one-quarter had tested more than twice. Among the 26 surveyed youth who reported that they were HIV-positive, 6 (23.1%) had AIDS at the time of diagnosis. Delays in care-seeking after diagnosis varied from a few months to seven years from time of test.</p> <p>Conclusion</p> <p>It is encouraging that many youth who had tested for HIV did so based on a realistic self-assessment of HIV risk behaviours; however, for others, a feeling of invulnerability was a barrier to testing. For those who tested positive, there was often a delay in accessing health services.</p
Search for CP violation in D+→ϕπ+ and D+s→K0Sπ+ decays
A search for CP violation in D + → ϕπ + decays is performed using data collected in 2011 by the LHCb experiment corresponding to an integrated luminosity of 1.0 fb−1 at a centre of mass energy of 7 TeV. The CP -violating asymmetry is measured to be (−0.04 ± 0.14 ± 0.14)% for candidates with K − K + mass within 20 MeV/c 2 of the ϕ meson mass. A search for a CP -violating asymmetry that varies across the ϕ mass region of the D + → K − K + π + Dalitz plot is also performed, and no evidence for CP violation is found. In addition, the CP asymmetry in the D+s→K0Sπ+ decay is measured to be (0.61 ± 0.83 ± 0.14)%
Measurement of the Λb0, Ξb-, and Ωb- Baryon Masses
Bottom baryons decaying to a J/ψ meson and a hyperon are reconstructed using 1.0 fb-1 of data collected in 2011 with the LHCb detector. Significant Λb0→J/ψΛ, Ξb-→J/ψΞ- and Ωb-→J/ψΩ- signals are observed and the corresponding masses are measured to be M(Λb0)=5619.53±0.13(stat.)±0.45(syst.) MeV/c2, M(Ξb-)=5795.8±0.9(stat.)±0.4(syst.) MeV/c2, M(Ωb-)=6046.0±2.2(stat.)±0.5(syst.) MeV/c2, while the differences with respect to the Λb0 mass are M(Ξb-)-M(Λb0)=176.2±0.9(stat.)±0.1(syst.) MeV/c2, M(Ωb-)-M(Λb0)=426.4±2.2(stat.)±0.4(syst.) MeV/c2. These are the most precise mass measurements of the Λb0, Ξb- and Ωb- baryons to date. Averaging the above Λb0 mass measurement with that published by LHCb using 35 pb-1 of data collected in 2010 yields M(Λb0)=5619.44±0.13(stat.)±0.38(syst.) MeV/c2
Test of lepton universality in decays
The first simultaneous test of muon-electron universality using
and decays is performed, in two ranges of the dilepton
invariant-mass squared, . The analysis uses beauty mesons produced in
proton-proton collisions collected with the LHCb detector between 2011 and
2018, corresponding to an integrated luminosity of 9 . Each
of the four lepton universality measurements reported is either the first in
the given interval or supersedes previous LHCb measurements. The
results are compatible with the predictions of the Standard Model.Comment: All figures and tables, along with any supplementary material and
additional information, are available at
https://cern.ch/lhcbproject/Publications/p/LHCb-PAPER-2022-046.html (LHCb
public pages
Precision measurement of violation in the penguin-mediated decay
A flavor-tagged time-dependent angular analysis of the decay
is performed using collision data collected
by the LHCb experiment at % at TeV, the center-of-mass energy of
13 TeV, corresponding to an integrated luminosity of 6 fb^{-1}. The
-violating phase and direct -violation parameter are measured
to be rad and
, respectively, assuming the same values
for all polarization states of the system. In these results, the
first uncertainties are statistical and the second systematic. These parameters
are also determined separately for each polarization state, showing no evidence
for polarization dependence. The results are combined with previous LHCb
measurements using collisions at center-of-mass energies of 7 and 8 TeV,
yielding rad and . This is the most precise study of time-dependent violation
in a penguin-dominated meson decay. The results are consistent with
symmetry and with the Standard Model predictions.Comment: All figures and tables, along with any supplementary material and
additional information, are available at
https://cern.ch/lhcbproject/Publications/p/LHCb-PAPER-2023-001.html (LHCb
public pages
First observation of a doubly charged tetraquark and its neutral partner
A combined amplitude analysis is performed for the decays and , which are
related by isospin symmetry. The analysis is based on data collected by the
LHCb detector in proton-proton collisions at center-of-mass energies of 7, 8
and 13. The full data sample corresponds to an integrated
luminosity of 9. Two new resonant states with masses of
and widths of
are observed, which decay to and
respectively. The former state indicates the first observation of
a doubly charged open-charm tetraquark state with minimal quark content
, and the latter state is a neutral tetraquark composed of
quarks. Both states are found to have spin-parity ,
and their resonant parameters are consistent with each other, which suggests
that they belong to an isospin triplet.Comment: All figures and tables, along with any supplementary material and
additional information, are available at
https://cern.ch/lhcbproject/Publications/p/LHCb-PAPER-2022-026.html (LHCb
public pages
Measurement of the differential branching fraction
The branching fraction of the rare decay is measured for the first time, in the squared dimuon mass
intervals, , excluding the and regions. The data
sample analyzed was collected by the LHCb experiment at center-of-mass energies
of 7, 8, and 13 TeV, corresponding to a total integrated luminosity of $9\
\mathrm{fb}^{-1}q^{2}q^{2} >15.0\
\mathrm{GeV}^2/c^4$, where theoretical predictions have the smallest model
dependence, agrees with the predictions.Comment: All figures and tables, along with any supplementary material and
additional information, are available at
https://cern.ch/lhcbproject/Publications/p/LHCb-PAPER-2022-050.html (LHCb
public pages
Measurement of the ratios of branching fractions R(D*) and R(D0)
The ratios of branching fractions
R
(
D
∗
)
≡
B
(
¯
B
→
D
∗
τ
−
¯
ν
τ
)
/
B
(
¯
B
→
D
∗
μ
−
¯
ν
μ
)
and
R
(
D
0
)
≡
B
(
B
−
→
D
0
τ
−
¯
ν
τ
)
/
B
(
B
−
→
D
0
μ
−
¯
ν
μ
)
are measured, assuming isospin symmetry, using a sample of proton-proton collision data corresponding to
3.0
fb
−
1
of integrated luminosity recorded by the LHCb experiment during 2011 and 2012. The tau lepton is identified in the decay mode
τ
−
→
μ
−
ν
τ
¯
ν
μ
. The measured values are
R
(
D
∗
)
=
0.281
±
0.018
±
0.024
and
R
(
D
0
)
=
0.441
±
0.060
±
0.066
, where the first uncertainty is statistical and the second is systematic. The correlation between these measurements is
ρ
=
−
0.43
. The results are consistent with the current average of these quantities and are at a combined 1.9 standard deviations from the predictions based on lepton flavor universality in the standard model
Search for rare decays of D0 mesons into two muons
A search for the very rare
D
0
→
μ
+
μ
−
decay is performed using data collected by the LHCb experiment in proton-proton collisions at
√
s
=
7
, 8, and 13 TeV, corresponding to an integrated luminosity of
9
fb
−
1
. The search is optimized for
D
0
mesons from
D
*
+
→
D
0
π
+
decays but is also sensitive to
D
0
mesons from other sources. No evidence for an excess of events over the expected background is observed. An upper limit on the branching fraction of this decay is set at
B
(
D
0
→
μ
+
μ
−
)
<
3.1
×
10
−
9
at a 90% C.L. This represents the world’s most stringent limit, constraining models of physics beyond the standard model
Precision measurement of CP violation in the penguin-mediated decay Bs0→ϕϕ
A flavor-tagged time-dependent angular analysis of the decay
B
0
s
→
ϕ
ϕ
is performed using
p
p
collision data collected by the LHCb experiment at the center-of-mass energy of 13 TeV, corresponding to an integrated luminosity of
6
fb
−
1
. The
C
P
-violating phase and direct
C
P
-violation parameter are measured to be
ϕ
s
¯
s
s
s
=
−
0.042
±
0.075
±
0.009
rad
and
|
λ
|
=
1.004
±
0.030
±
0.009
, respectively, assuming the same values for all polarization states of the
ϕ
ϕ
system. In these results, the first uncertainties are statistical and the second systematic. These parameters are also determined separately for each polarization state, showing no evidence for polarization dependence. The results are combined with previous LHCb measurements using
p
p
collisions at center-of-mass energies of 7 and 8 TeV, yielding
ϕ
s
¯
s
s
s
=
−
0.074
±
0.069
rad
and
|
λ
|
=
1.009
±
0.030
. This is the most precise study of time-dependent
C
P
violation in a penguin-dominated
B
meson decay. The results are consistent with
C
P
symmetry and with the standard model predictions
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