12 research outputs found
Radiative proton-antiproton annihilation to a lepton pair
The annihilation of proton and antiproton to electron-positron pair,
including radiative corrections due to the emission of virtual and real photons
is considered. The results are generalized to leading and next-to leading
approximations. The relevant distributions are derived and numerical
applications are given in the kinematical range accessible to the PANDA
experiment at the FAIR facility.Comment: 2 figure
On masses of unstable particles and their antiparticles in the CPT-invariant system
We show that the diagonal matrix elements of the effective Hamiltonian
governing the time evolution in the subspace of states of an unstable particle
and its antiparticle need not be equal at ( is the instant
of creation of the pair) when the total system under consideration is CPT
invariant but CP noninvariant. To achieve this we use the transition amplitudes
for transitions , together
with the identity expressing the effective Hamiltonian by these amplitudes and
their derivatives with respect to time . This identity must be fulfilled by
any effective Hamiltonian (both approximate and exact) derived for the two
state complex. The unusual consequence of this result is that, contrary to the
properties of stable particles, the masses of the unstable particle "1" and its
antiparticle "2" need not be equal for in the case of preserved
CPT and violated CP symmetries.Comment: LaTex2e, 17 pages, new comments and references adde
Patients with chronic neck pain demonstrate altered patterns of muscle activation during performance of a functional upper limb task
Study Design. Cross-sectional study. Objective. This study compared neck muscle activation patterns during and after a repetitive upper limb task between patients with idiopathic neck pain, whiplash-associated disorders, and controls. Summary of Background Data. Previous studies have identified altered motor control of the upper trapezius during functional tasks in patients with neck pain. Whether the cervical flexor muscles demonstrate altered motor control during functional activities is unknown. Methods. Electromyographic activity was recorded from the sternocleidomastoid, anterior scalenes, and upper trapezius muscles. Root mean square electromyographic amplitude was calculated during and on completion of a functional task. Results. A general trend was evident to suggest greatest electromyograph amplitude in the sternocleidomastoid, anterior scalenes, and left upper trapezius muscles for the whiplash-associated disorders group, followed by the idiopathic group, with lowest electromyographic amplitude recorded for the control group. A reverse effect was apparent for the right upper trapezius muscle. The level of perceived disability ( Neck Disability Index score) had a significant effect on the electromyographic amplitude recorded between neck pain patients. Conclusions. Patients with neck pain demonstrated greater activation of accessory neck muscles during a repetitive upper limb task compared to asymptomatic controls. Greater activation of the cervical muscles in patients with neck pain may represent an altered pattern of motor control to compensate for reduced activation of painful muscles. Greater perceived disability among patients with neck pain accounted for the greater electromyographic amplitude of the superficial cervical muscles during performance of the functional task
Polarisation experiments to test t- and cpt- invariance in nucleon-nucleon and nucleon-antinucleon scattering
The Production of the Exotic Atoms , and
Estimates are made of the signals to be expected in the production of the
exotic atoms Pionium (), Kaonium () and also in
pp, pd and reactions. Such experiments are now being undertaken or
contemplated at CELSIUS, COSY, Indiana and SATURNE.Comment: 20 pages Latex, Bib-sty included and 3 figures on request from AM