New Analysis of the Delta I = 1/2 Rule in Kaon Decays and the B_K Parameter

We present a new analysis of the Delta I = 1/2 rule in K --> pi pi decays and the B_K parameter. We use the 1/N_c expansion within the effective chiral lagrangian for pseudoscalar mesons and compute the hadronic matrix elements at leading and next-to-leading order in the chiral and the 1/N_c expansions. Numerically, our calculation reproduces the dominant Delta I = 1/2 K --> pi pi amplitude. Our result depends only moderately on the choice of the cutoff scale in the chiral loops. The Delta I = 3/2 amplitude emerges sufficiently suppressed but shows a significant dependence on the cutoff. The B_K parameter turns out to be smaller than the value previously obtained in the 1/N_c approach. It also shows a significant dependence on the choice of the cutoff scale. Our results indicate that corrections from higher order terms and/or higher resonances are large for the Delta I = 3/2 K --> pi pi amplitude and the (|Delta S| = 2) K^0 -- anti K^0 transition amplitude.Comment: 50 pages, LaTeX, 13 eps figure

Analyzing epsilon'/epsilon in the 1/N_c Expansion

We present a recent analysis of epsilon'/epsilon in the 1/N_c expansion. We show that the 1/N_c corrections to the matrix element of Q_6 are large and positive, indicating a Delta I=1/2 enhancement similar to the one of Q_1 and Q_2 which dominate the CP conserving amplitude. This enhances the CP ratio and can bring the standard model prediction close to the measured value for central values of the parameters.Comment: One reference corrected. 5 pages, talk presented by P.H. Soldan at the 3. International Conference on B Physics and CP Violation, Taipei, Taiwan, December 3 - 7, 1999. Slightly expanded version of the article submitted to the proceeding

Views and experiences of men who have sex with men on the ban on blood donation: a cross sectional survey with qualitative interviews.

OBJECTIVE: To explore compliance with the UK blood services' criterion that excludes men who have had penetrative sex with a man from donating blood, and to assess the possible effects of revising this policy. DESIGN: A random location, cross sectional survey followed by qualitative interviews. SETTING: Britain. PARTICIPANTS: 1028 of 32,373 men in the general population reporting any male sexual contact completed the survey. Additional questions were asked of a general population sample (n=3914). Thirty men who had had penetrative sex with a man participated in the qualitative interviews (19 who had complied with the blood services' exclusion criterion and 11 who had not complied). Main outcome measure Compliance with the blood services' lifetime exclusion criterion for men who have had penetrative sex with a man. RESULTS: 10.6% of men with experience of penetrative sex with a man reported having donated blood in Britain while ineligible under the exclusion criterion, and 2.5% had donated in the previous 12 months. Ineligible donation was less common among men who had had penetrative sex with a man recently (in previous 12 months) than among men for whom this last occurred longer ago. Reasons for non-compliance with the exclusion included self categorisation as low risk, discounting the sexual experience that barred donation, belief in the infallibility of blood screening, concerns about confidentiality, and misunderstanding or perceived inequity of the rule. Although blood donation was rarely viewed as a "right," potential donors were seen as entitled to a considered assessment of risk. A one year deferral since last male penetrative sex was considered by study participants to be generally feasible, equitable, and acceptable. CONCLUSIONS: A minority of men who have sex with men who are ineligible to donate blood under the current donor exclusion in Britain have nevertheless done so in the past 12 months. Many of the reasons identified for non-compliance seem amenable to intervention. A clearly rationalised and communicated one year donor deferral is likely to be welcomed by most men who have sex with men

Ultracold Li + Li₂ collisions: Bosonic and fermionic cases

We have carried out quantum dynamical calculations of vibrational quenching in Li Li2 collisions for both bosonic 7Li and fermionic 6Li. These are the first ever such calculations involving fermionic atoms. We find that for the low initial vibrational states considered here (v 3), the quenching rates are not suppressed for fermionic atoms. This contrasts with the situation found experimentally for molecules formed via Feshbach resonances in very high vibrational states

Oral human papillomavirus (HPV) infection in men who have sex with men: prevalence and lack of anogenital concordance.

To estimate the prevalence of oral detectable human papillomavirus (HPV) DNA in HIV-negative men who have sex with men (MSM) attending a sexual health clinic in London and concordance with anogenital HPV infection. Such data are important to improve our understanding of the epidemiology of oral HPV and the potential use of vaccines to prevent oropharyngeal cancers