1,003 research outputs found
Factorization in the Production and Decay of the X(3872)
The production and decay of the X(3872) are analyzed under the assumption
that the X is a weakly-bound molecule of the charm mesons D^0 \bar D^{*0} and
D^{*0} \bar D^0. The decays imply that the large D^0 \bar D^{*0} scattering
length has an imaginary part. An effective field theory for particles with a
large complex scattering length is used to derive factorization formulas for
production rates and decay rates of X. If a partial width is calculated in a
model with a particular value of the binding energy, the factorization formula
can be used to extrapolate to other values of the binding energy and to take
into account the width of the X. The factorization formulas relate the rates
for production of X to those for production of D^0 \bar D^{*0} and D^{*0} \bar
D^0 near threshold. They also imply that the line shape of X differs
significantly from that of a Breit-Wigner resonance.Comment: 23 pages, 8 figures, revtex4, typos correcte
Pion Interactions in the X(3872)
We consider pion interactions in an effective field theory of the narrow
resonance X(3872), assuming it is a weakly bound molecule of the charm mesons
D^{0} \bar D^{*0} and D^{*0} \bar D^{0}. Since the hyperfine splitting of the
D^{0} and D^{*0} is only 7 MeV greater than the neutral pion mass, pions can be
produced near threshold and are non-relativistic. We show that pion exchange
can be treated in perturbation theory and calculate the next-to-leading-order
correction to the partial decay width \Gamma[X \to D^0 \bar D^{0} \pi^0].Comment: 26 pages, 11 figures, revtex4, to appear in Phys. Rev.
Production of the X(3872) in B Meson Decay by the Coalescence of Charm Mesons
If the recently-discovered charmonium state X(3872) is a loosely-bound S-wave
molecule of the charm mesons \bar D^0 D^{*0} or \bar D^{*0} D^0, it can be
produced in B meson decay by the coalescence of charm mesons. If this
coalescence mechanism dominates, the ratio of the differential rate for B^+ \to
\bar D^0 D^{*0} K^+ near the \bar D^0 D^{*0} threshold and the rate for B^+ \to
X K^+ is a function of the \bar D^0 D^{*0} invariant mass and hadron masses
only. The identification of the X(3872) as a \bar D^0 D^{*0}/\bar D^{*0} D^0
molecule can be confirmed by observing an enhancement in the \bar D^0 D^{*0}
invariant mass distribution near the threshold. An estimate of the branching
fraction for B^+ \to X K^+ is consistent with observations if X has quantum
numbers J^{PC} = 1^{++} and if J/\psi \pi^+ \pi^- is one of its major decay
modes.Comment: 4 pages, 3 figures, revtex
Quahogs in Eastern North America: Part II, History by Province and State
The northern quahog, Mercenaria mercenaria, ranges along the
Atlantic Coast of North America from the Canadian Maritimes to Florida, while the southern quahog, M. campechiensis,
ranges mostly from Florida to southern Mexico. The northern quahog was fished by native North Americans during prehistoric periods. They used the meats as food and the shells as scrapers and as utensils. The European colonists copied the Indians treading method, and they also used short
rakes for harvesting quahogs. The Indians of southern New England and Long Island, N.Y., made wampum from quahog shells, used it for ornaments and sold it to the colonists, who, in turn, traded it to other Indians for furs. During the late 1600’s, 1700’s, and 1800’s, wampum was made in small factories for eventual trading with Indians farther west for furs.
The quahoging industry has provided people in many coastal communities with a means of earning a livelihood and has
given consumers a tasty, wholesome food whether eaten raw, steamed, cooked in chowders, or as stuffed quahogs. More than a dozen methods and types of gear have been used in the last two centuries for harvesting quahogs. They include treading and using various types of rakes and dredges,
both of which have undergone continuous improvements in design. Modern dredges are equipped with hydraulic jets and one type has an escalator to bring the quahogs continuously to the boats. In the early 1900’s, most provinces and states
established regulations to conserve and maximize yields of their quahog stocks. They include a minimum size, now almost
universally a 38-mm shell width, and can include gear limitations and daily quotas.
The United States produces far more quahogs than either Canada or Mexico. The leading producer in Canada is Prince
Edward Island. In the United States, New York, New Jersey, and Rhode Island lead in quahog production in the north, while Virginia and North Carolina lead in the south. Connecticut and Florida were large producers in the 1990’s. The State of Tabasco leads in Mexican production. In the northeastern United States, the bays with large openings, and thus large exchanges of bay waters with ocean waters,
have much larger stocks of quahogs and fisheries than bays with small openings and water exchanges.
Quahog stocks in certified beds have been enhanced by transplanting stocks to them from stocks in uncertified waters and by planting seed grown in hatcheries, which grew in number from Massachusetts to Florida in the 1980’s and 1990’s
Simple test for high Jc and low Rs superconducting thin films
A simple method, fishing high-Tc superconductor thin films out of liquid
nitrogen bath by a permanent magnet (field > Hc1) due to the effect of high
flux pinning, has been suggested to identify films having high critical current
density (Jc > 106 A/cm2 at 77 K) and thus a low microwave surface resistance
(Rs). We have demonstrated that a Nd-Fe-B magnet, having a maximum field of ~
0.5 T, could fish out Tl-1223 superconducting thin films on LSAT substrate with
a thickness of ~ 5000 Angstrong having Jc > 1 MA/cm2 (at 77 K) whereas it could
not fish out other films with Jc < 0.1 MA/cm2 at 77 K. The fished out films
exhibit Rs values 237 - 245 ((at 77 K and 10 GHz, which is lower than that (Rs
= 317 (() of the best YBCO film at the same temperature and frequency. On the
other hand, the non-fishable films show very high Rs values. This method is a
very simple tool to test for high Jc and good microwave properties of
superconducting films of large area which otherwise require a special and
expensive tool.Comment: 5 pages including 2 figures, to be published as Rapid Commun. in
Supercond. Sci. Techno
Intimate Relationship Dynamics and Changing Desire for Pregnancy Among Young Women
Peer Reviewedhttps://deepblue.lib.umich.edu/bitstream/2027.42/151900/1/psrh12119_am.pdfhttps://deepblue.lib.umich.edu/bitstream/2027.42/151900/2/psrh12119.pd
Contraceptive Desert? Black-White Differences in Characteristics of Nearby Pharmacies
Objectives: Race differences in contraceptive use and in geographic access to pharmacies are well established. We explore race differences in characteristics of nearby pharmacies that are likely to facilitate (or not) contraceptive purchase.
Study design: We conducted analyses with two geocode-linked datasets: (1) the Relationship Dynamics and Social Life (RDSL) project, a study of a random sample of 1003 women ages 18-19 living in a county in Michigan in 2008-09; and (2) the Community Pharmacy Survey, which collected data on 82 pharmacies in the county in which the RDSL study was conducted.
Results: Although young African-American women tend to live closer to pharmacies than their white counterparts (1.2 miles to the nearest pharmacy for African Americans vs. 2.1 miles for whites), those pharmacies tend to be independent pharmacies (59 vs. 16%) that are open fewer hours per week (64.6 vs. 77.8) and have fewer female pharmacists (17 vs. 50%), fewer patient brochures on contraception (2 vs. 5%), more difficult access to condoms (49% vs. 85% on the shelf instead of behind glass, behind the counter, or not available), and fewer self-check-out options (3 vs. 9%). More African-American than white women live near African-American pharmacists (8 vs. 3%). These race differences are regardless of poverty, measured by the receipt of public assistance.
Conclusions: Relative to white women, African-American women may face a contraception desert, wherein they live nearer to pharmacies, but those pharmacies have characteristics that may impede the purchase of contraception
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