On the strange quark mass with improved staggered quarks

We present results on the sum of the masses of light and strange quark using improved staggered quarks. Our calculation uses 2+1 flavours of dynamical quarks. The effects of the dynamical quarks are clearly visible.Comment: Lattice2002(spectrum) Latex 3 pages, 2 figure

Role of persistent processus vaginalis in hydroceles found in a tropical population

Background: Lymphatic obstruction by Wuchereria bancrofti is thought to be the mechanism for development of tropical hydrocele in men and for elephantiasis, mostly in women. Hydrocele prevalence is used to determine the effectiveness of parasite eradication programs. Methods: We maintained a prospective log of operations performed at 1 Canadian Field Hospital during its relief mission to Léogâne, Haiti. Information regarding duration of symptoms, type of previous surgery (if any), surgical approach, associated inguinal hernia and volume and appearance of hydrocele fluid in patients with tropical hydroceles were recorded. Results: From January to March 2010, 4922 patients were seen, none of whom had elephantiasis. Of the 64 patients who collectively underwent 69 inguino-scrotal procedures, 5 patients had inguinal hernia repair several years after hydrocele excision via the scrotum, 19 patients with bilateral hydroceles underwent a scrotum-only approach, and 45 patients had an inguinal approach (33 unilateral and 12 bilateral) to repair 57 hydroceles. A patent processus vaginalis was present in 50 of 57 (88%) hydroceles where the groin was explored. Conclusion: Hydroceles remain common in Léogâne despite successful eradication of filariasis with mass drug administration using diethylcarbamazine-fortified cooking salt. Persistent patent processus vaginalis is a more likely cause than persistent filariasis. There is probably little difference between hydrocele in developed countries and tropical hydrocele other than neglect. Hydrocele prevalence is not a measure of the effectiveness of parasite eradication programs. The recent earthquake in Haiti has highlighted not only the response required for such disasters, but also the ongoing battle against endemic diseases, such as lymphatic filariasis. 1 Canadian Field Hospital was deployed to Léogâne, the epicentre of the earthquake, on Jan. 12, 2010. Wuchereria bancrofti, the most common causative organism of lymphatic filariasis, was endemic in the Léogâne area until eradication by mass drug administration using diethylcarbamazine (DEC) in cooking salt.1 Once the injured were cared for, the surgical needs of the community were addressed. Large numbers of male patients came to our hospital seeking help for disabling hydroceles. Hydroceles in a tropical population, sometimes called tropical hydroceles, are distinguished from those seen in temperate zones by their high prevalence and massive size. Lymphatic obstruction is thought to be the mechanism for development of tropical hydrocele.2 Eradication of the parasite and excision of the hydrocele sac via a scrotal incision is the preferred management.2 In Canada, hydroceles in children are approached through an inguinal incision so that the associated hernia can be controlled, whereas the scrotal approach is primarily used in adults to excise the sac and evert the remnant. Initially, we treated children using the inguinal approach. We then operated on several adults with symptomatic inguinal hernias whose ipsilateral hydroceles had previously been excised via the scrotal approach. We became concerned that adult patients with hydroceles in Haiti had persistence of the processus vaginalis, which had been neglected since childhood. We decided to use the inguinal approach to treat hydroceles in adults if time and resources permitted

Highly Improved Staggered Quarks on the Lattice, with Applications to Charm Physics

We use perturbative Symanzik improvement to create a new staggered-quark action (HISQ) that has greatly reduced one-loop taste-exchange errors, no tree-level order a^2 errors, and no tree-level order (am)^4 errors to leading order in the quark's velocity v/c. We demonstrate with simulations that the resulting action has taste-exchange interactions that are at least 3--4 times smaller than the widely used ASQTAD action. We show how to estimate errors due to taste exchange by comparing ASQTAD and HISQ simulations, and demonstrate with simulations that such errors are no more than 1% when HISQ is used for light quarks at lattice spacings of 1/10 fm or less. The suppression of (am)^4 errors also makes HISQ the most accurate discretization currently available for simulating c quarks. We demonstrate this in a new analysis of the psi-eta_c mass splitting using the HISQ action on lattices where a m_c=0.43 and 0.66, with full-QCD gluon configurations (from MILC). We obtain a result of~111(5) MeV which compares well with experiment. We discuss applications of this formalism to D physics and present our first high-precision results for D_s mesons.Comment: 21 pages, 8 figures, 5 table

Update: Accurate Determinations of alpha_s from Realistic Lattice QCD

We use lattice QCD simulations, with MILC configurations (including vacuum polarization from u, d, and s quarks), to update our previous determinations of the QCD coupling constant. Our new analysis uses results from 6 different lattice spacings and 12 different combinations of sea-quark masses to significantly reduce our previous errors. We also correct for finite-lattice-spacing errors in the scale setting, and for nonperturbative chiral corrections to the 22 short-distance quantities from which we extract the coupling. Our final result is alpha_V(7.5GeV,nf=3) = 0.2120(28), which is equivalent to alpha_msbar(M_Z,n_f=5)= 0.1183(8). We compare this with our previous result, which differs by one standard deviation.Comment: 12 pages, 2 figures, 4 table

Precise charm to strange mass ratio and light quark masses from full lattice QCD

By using a single formalism to handle charm, strange and light valence quarks in full lattice QCD for the first time, we are able to determine ratios of quark masses to 1%. For $m_c/m_s$ we obtain 11.85(16), an order of magnitude more precise than the current PDG average. Combined with 1% determinations of the charm quark mass now possible this gives $\bar{m}_s(2{\rm GeV}) =$ 92.4(1.5) MeV. The MILC result for $m_s/m_l = 27.2(3)$ yields $\bar{m}_l(2{\rm GeV})$ = 3.40(7) MeV for the average of $u$ and $d$ quark masses.Comment: 4 pages, 2 figures. Version accepted by Physical Review Letters. Changes include modifying the title, using the MILC value for m_s/m_l which changes slightly the resulting up and down quark masses and their average, adding some references and making other small adjustments to the text for space reasons

Direct determination of the strange and light quark condensates from full lattice QCD

We determine the strange quark condensate from lattice QCD for the first time and compare its value to that of the light quark and chiral condensates. The results come from a direct calculation of the expectation value of the trace of the quark propagator followed by subtraction of the appropriate perturbative contribution, derived here, to convert the non-normal-ordered mψ̅ ψ to the MS̅ scheme at a fixed scale. This is then a well-defined physical “nonperturbative” condensate that can be used in the operator product expansion of current-current correlators. The perturbative subtraction is calculated through O(αs) and estimates of higher order terms are included through fitting results at multiple lattice spacing values. The gluon field configurations used are “second generation” ensembles from the MILC collaboration that include 2+1+1 flavors of sea quarks implemented with the highly improved staggered quark action and including u/d sea quarks down to physical masses. Our results are ⟨s̅ s⟩MS̅ (2  GeV)=-(290(15)  MeV)3, ⟨l̅ l⟩MS̅ (2  GeV)=-(283(2)  MeV)3, where l is a light quark with mass equal to the average of the u and d quarks. The strange to light quark condensate ratio is 1.08(16). The light quark condensate is significantly larger than the chiral condensate in line with expectations from chiral analyses. We discuss the implications of these results for other calculations

Constrained Curve Fitting

We survey techniques for constrained curve fitting, based upon Bayesian statistics, that offer significant advantages over conventional techniques used by lattice field theorists.Comment: Lattice2001(plenary); plenary talk given by G.P. Lepage at Lattice 2001 (Berlin); 9 pages, 5 figures (postscript specials

Improvement and Taste Symmetry Breaking for Staggered Quarks

We compare several improved actions for staggered quarks. We study the effect of improvement on the taste changing interactions by calculating the splitting in the pion spectrum. We investigate the effect of the improvement on some topological properties.Comment: 3 pages, 3 figures, Lattice 2003 proceeding