Large experimental programmes in the fields of nuclear and particle physics search for evidence of physics beyond that explained by current theories. The observation of the Higgs boson completed the ...set of particles predicted by the standard model, which currently provides the best description of fundamental particles and forces. However, this theory's limitations include a failure to predict fundamental parameters, such as the mass of the Higgs boson, and the inability to account for dark matter and energy, gravity, and the matter-antimatter asymmetry in the Universe, among other phenomena. These limitations have inspired searches for physics beyond the standard model in the post-Higgs era through the direct production of additional particles at high-energy accelerators, which have so far been unsuccessful. Examples include searches for supersymmetric particles, which connect bosons (integer-spin particles) with fermions (half-integer-spin particles), and for leptoquarks, which mix the fundamental quarks with leptons. Alternatively, indirect searches using precise measurements of well predicted standard-model observables allow highly targeted alternative tests for physics beyond the standard model because they can reach mass and energy scales beyond those directly accessible by today's high-energy accelerators. Such an indirect search aims to determine the weak charge of the proton, which defines the strength of the proton's interaction with other particles via the well known neutral electroweak force. Because parity symmetry (invariance under the spatial inversion (x, y, z) → (-x, -y, -z)) is violated only in the weak interaction, it provides a tool with which to isolate the weak interaction and thus to measure the proton's weak charge
. Here we report the value 0.0719 ± 0.0045, where the uncertainty is one standard deviation, derived from our measured parity-violating asymmetry in the scattering of polarized electrons on protons, which is -226.5 ± 9.3 parts per billion (the uncertainty is one standard deviation). Our value for the proton's weak charge is in excellent agreement with the standard model
and sets multi-teraelectronvolt-scale constraints on any semi-leptonic parity-violating physics not described within the standard model. Our results show that precision parity-violating measurements enable searches for physics beyond the standard model that can compete with direct searches at high-energy accelerators and, together with astronomical observations, can provide fertile approaches to probing higher mass scales.
The Q(weak) experiment has measured the parity-violating asymmetry in ep elastic scattering at Q(2)=0.025(GeV/c)(2), employing 145 μA of 89% longitudinally polarized electrons on a 34.4 cm long ...liquid hydrogen target at Jefferson Lab. The results of the experiment's commissioning run, constituting approximately 4% of the data collected in the experiment, are reported here. From these initial results, the measured asymmetry is A(ep)=-279±35 (stat) ± 31 (syst) ppb, which is the smallest and most precise asymmetry ever measured in ep scattering. The small Q(2) of this experiment has made possible the first determination of the weak charge of the proton Q(W)(p) by incorporating earlier parity-violating electron scattering (PVES) data at higher Q(2) to constrain hadronic corrections. The value of Q(W)(p) obtained in this way is Q(W)(p)(PVES)=0.064±0.012, which is in good agreement with the standard model prediction of Q(W)(p)(SM)=0.0710±0.0007. When this result is further combined with the Cs atomic parity violation (APV) measurement, significant constraints on the weak charges of the up and down quarks can also be extracted. That PVES+APV analysis reveals the neutron's weak charge to be Q(W)(n)(PVES+APV)=-0.975±0.010.
Clinical Outcomes and Insulin Secretion After Islet Transplantation With the Edmonton Protocol
Edmond A. Ryan 1 ,
Jonathan R.T. Lakey 2 ,
Ray V. Rajotte 2 ,
Gregory S. Korbutt 2 ,
Tatsuya Kin 2 ,
...Sharleen Imes 4 ,
Alex Rabinovitch 1 ,
John F. Elliott 3 ,
David Bigam 2 ,
Norman M. Kneteman 2 ,
Garth L. Warnock 2 ,
Ingrid Larsen 4 and
A.M. James Shapiro 2
1 Department of Medicine, the
2 Department of Surgery, Surgical Medical Research Institute, and the
3 Department of Medical Microbiology and Infectious Diseases, University of Alberta
4 Capital Health Authority, Edmonton, Alberta
Abstract
Islet transplantation offers the prospect of good glycemic control without major surgical risks. After our initial report
of successful islet transplantation, we now provide further data on 12 type 1 diabetic patients with brittle diabetes or problems
with hypoglycemia previous to 1 November 2000. Details of metabolic control, acute complications associated with islet transplantation,
and long-term complications related to immunosuppression therapy and diabetes were noted. Insulin secretion, both acute and
over 30 min, was determined after intravenous glucose tolerance tests (IVGTTs). The median follow-up was 10.2 months (CI 6.5–17.4),
and the longest was 20 months. Glucose control was stable, with pretransplant fasting and meal tolerance–stimulated glucose
levels of 12.5 ± 1.9 and 20.0 ± 2.7 mmol/l, respectively, but decreased significantly, with posttransplant levels of 6.3 ±
0.3 and 7.5 ± 0.6 mmol/l, respectively ( P < 0.006). All patients have sustained insulin production, as evidenced by the most current baseline C-peptide levels 0.66
± 0.06 nmol/l, increasing to 1.29 ± 0.25 nmol/l 90 min after the meal-tolerance test. The mean HbA 1c level decreased from 8.3 ± 0.5% to the current level of 5.8 ± 0.1% ( P < 0.001). Presently, four patients have normal glucose tolerance, five have impaired glucose tolerance, and three have post–islet
transplant diabetes (two of whom need oral hypoglycemic agents and low-dose insulin (<10 U/day). Three patients had a temporary
increase in their liver-function tests. One patient had a thrombosis of a peripheral branch of the right portal vein, and
two of the early patients had bleeding from the hepatic needle puncture site; but these technical problems were resolved.
Two patients had transient vitreous hemorrhages. The two patients with elevated creatinine levels pretransplant had a significant
increase in serum creatinine in the long term, although the mean serum creatinine of the group was unchanged. The cholesterol
increased in five patients, and lipid-lowering therapy was required for three patients. No patient has developed cytomegalovirus
infection or disease, posttransplant lymphoproliferative disorder, malignancies, or serious infection to date. None of the
patients have been sensitized to donor antigen. In 11 of the 12 patients, insulin independence was achieved after 9,000 islet
equivalents (IEs) per kilogram were transplanted. The acute insulin response and the insulin area under the curve (AUC) after
IVGTT were consistently maintained over time. The insulin AUC from the IVGTT correlated to the number of islets transplanted,
but more closely correlated when the cold ischemia time was taken into consideration ( r = 0.83, P < 0.001). Islet transplantation has successfully corrected labile type 1 diabetes and problems with hypoglycemia, and our
results show persistent insulin secretion. After a minimum of 9,000 IEs per kilogram are provided, insulin independence is
usually attained. An elevation of creatinine appears to be a contraindication to this immunosuppressive regimen. For the subjects
who had labile type 1 diabetes that was difficult to control, the risk-to-benefit ratio is in favor of islet transplantation.
AIRg, acute insulin response to glucose
AUC, area under the curve, AUCC-p, AUC for C-peptide above baseline
AUCg, AUC for glucose above baseline
AUCi, AUC for insulin above baseline
CMV, cytomegalovirus
HOMA, homeostasis model assessment
IE, islet equivalent
IGT, impaired glucose tolerance
IVGTT, intravenous glucose tolerance test
KG, the rate of glucose disposal
OGTT, oral glucose tolerance test
MAGE, mean amplitude of glycemic excursion
WBC, white blood cell count
Footnotes
Address correspondence and reprint requests to Edmond A. Ryan, Department of Medicine, 362 Heritage Medical Research Centre,
University of Alberta, Edmonton, Alberta, Canada T6G 2S2. E-mail: edmond.ryan{at}ualberta.ca .
Received for publication 5 December 2000 and accepted in revised form 31 January 2001. Posted at www.diabetes.org/diabetes on 7 March 2001.
A beam-normal single-spin asymmetry generated in the scattering of transversely polarized electrons from unpolarized nucleons is an observable related to the imaginary part of the two-photon exchange ...process. We report a 2% precision measurement of the beam-normal single-spin asymmetry in elastic electron-proton scattering with a mean scattering angle of θlab=7.9° and a mean energy of 1.149 GeV. The asymmetry result is Bn=−5.194±0.067(stat)±0.082 (syst) ppm. This is the most precise measurement of this quantity available to date and therefore provides a stringent test of two-photon exchange models at far-forward scattering angles (θlab→0) where they should be most reliable.
Multiplicities of charged hadrons produced in deep inelastic muon scattering off a
6
LiD target have been measured as a function of the DIS variables
x
Bj
,
Q
2
,
W
2
and the final state hadron ...variables
p
T
and
z
. The
distributions are fitted with a single exponential function at low values of
to determine the dependence of
on
x
Bj
,
Q
2
,
W
2
and
z
. The
z
-dependence of
is shown to be a potential tool to extract the average intrinsic transverse momentum squared of partons,
, as a function of
x
Bj
and
Q
2
in a leading order QCD parton model.
Celotno besedilo
Dostopno za:
DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
A sandwich detector composed of scintillator and steel-covered lead layers was introduced in the fixed-target COMPASS experiment at CERN for vetoing events not completely covered by the two-stage ...magnetic spectrometer. Wavelength shifting fibres glued into grooves in the scintillator tiles serve for fast readout. Minimum ionising particles impinging on the 2
m ×2
m detector outside of a central hole, sparing the spectrometer's entry, are detected with a probability of 98%. The response to charged particles and photons is modelled in detail in Monte Carlo calculations. Figures of merit of the veto trigger in 190
GeV/
c
π
−
+
p
(or nucleus) experiments are an enrichment of exclusive events in the recorded data by a factor of 3.5 and a false-veto probability of 1%.
In this paper, we report the first measurement of the parity-violating elastic electron scattering asymmetry on 27Al. The 27Al elastic asymmetry is $A_{\text{PV}}$ = 2.16 ± 0.11(stat) ± 0.16(syst) ...ppm, and was measured at $\langle Q^2\rangle$ = 0.02357 ± 0.00010 GeV$^2$, $\angleθ_{\text{lab}}$ = 7.61° ± 0.02°, and $\langle E_{\text{lab}}$ = 1.157 GeV with the Qweak apparatus at Jefferson Lab. Predictions using a simple Born approximation as well as more sophisticated distorted-wave calculations are in good agreement with this result. From this asymmetry the 27Al neutron radius $R_n$ = 2.89 ± 0.12 fm was determined using a many-models correlation technique. The corresponding neutron skin thickness $R_n – R_p$ = –0.04 ± 0.12 fm is small, as expected for a light nucleus with a neutron excess of only 1. This result thus serves as a successful benchmark for electroweak determinations of neutron radii on heavier nuclei. A tree-level approach was used to extract the 27Al weak radius $R_w$ = 3.00 ± 0.15 fm, and the weak skin thickness $R_{\text{wk}} – R_{\text{ch}}$ = –0.04 ± 0.15 fm. The weak form factor at this $Q^2$ is $F_{\text{wk}}$ = 0.39 ± 0.04.
We report measurements of the parity-conserving beam-normal single-spin elastic scattering asymmetries Bn on 12C and 27Al, obtained with an electron beam polarized transverse to its momentum ...direction. These measurements add an additional kinematic point to a series of previous measurements of Bn on 12C and provide a first measurement on 27Al. The experiment utilized the Qweak apparatus at Jefferson Lab with a beam energy of 1.158 GeV. The average lab scattering angle for both targets was 7.7°, and the average Q2 for both targets was 0.02437 GeV2 (Q = 0.1561 GeV). The asymmetries are Bn = -10.68 ± 0.90 (stat) ± 0.57 (syst) ppm 12C and Bn = -12.16 ± 0.58 (stat) ± 0.62 (syst) ppm for 27Al. The results are consistent with theoretical predictions, and are compared to existing data. When scaled by Z/A, the Q dependence of all the far-forward angle (θ < 10°) data from 1H to 27Al can be described by the same slope out to Q ≈ 0.35 GeV. Larger-angle data from other experiments in the same Q range are consistent with a slope about twice as steep.
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