I'm trying to understand why the Bc meson (anti b and c) has a lifetime of 0.46 picoseconds whilst the Bs, B+ and B- have lifetimes of ~1.6 picoseconds. Is this a density of states thing? or to do with the CKM elements?
Thanks for any help.
Hi,
I graduate university this summer with a physics degree, (4 year masters, specialising in astrophysics and particle physics), and I'm very keen to do a PhD in cosmology. Does anyone know which departments are the best to work in, for this field? I'd love a project on QSOs as a probe of...
Homework Statement
You are observing a high redshift (z ≥ 5) quasar. Suppose that there are n(z) = n_{0}(1+z)^3 damped Lyman-alpha (DLA) clouds per Mpc3 at redshift z, each with cross-sectional area a. Explain why we expect to see through n(z)al of them along a length l of the path towards...
Homework Statement
The Plummer sphere of total mass M and scale radius a is a simple if crude model for
star clusters and round galaxies. Its gravitational potential:
\phi(r) = -GM / (r^2 +a^2)^{1/2}
approaches that of a point mass for r >> a
Find the density of the sphere as a function of...
Homework Statement
(The question is about micro vertex detectors, but I've distilled it into what needs to be done)
You have two points (x1,y1 and x2,y2), assumed to lie on a straight line. The points have a one sigma uncertainty of d. x1 and x2 are separated by a distance L (much greater...
I'm doing some work on schwarzchild orbits, and everything assumes that \theta=\pi/2 and claims that this doesn't compromise generality. It seems pretty obvious (since all the geodesics are planar or radial and the metric is spherically symmetric), but can anyone prove that \theta=\pi/2 is fully...
Thanks. Given that's the case then z''=\ddot{z}/\dot{t}^2=g(1+gz) can't be true (since this is the wrong answer).
I can't see any thing wrong for \dot{t}:
whats wrong with:
L = (1+gz)^2dt^2-dx^2-dy^2-dz^2)
therefore by EL:
(d/ds)(2\dot{t}(1+gz)^2) =0
so
\dot{t} (1+gz)^2 = constant
Update: I've now solved it using the Christoffel symbols, but am still confused as to why the Euler-Lagrange method hasn't worked.This is wrong:
\ddot{z} = -g{\dot{t}^2}(1+gz) (1)
It should read:
\ddot{z} =-g{\dot{t}^2}/(1+gz) (2)
I got (1) direct from the EL equation
-2\ddot{z} -...
Yes the 2 is wrong. My apologies.
For the mu = 0 equation I have:
(d/ds)(2\dot{t}(1+gz)^2) =0
thus
\dot{t} (1+gz)^2 = constant
also
\ddot{z} = \dot{t}d\dot{z}/dt = \dot{t}(d/dt)(\dot{t}z') = \dot{t}(z'(d\dot{t})/dt +\dot{t}z'')=\dot{t}^2z''+\ddot{t}z'
I'm doing some revision for a General relativity exam, and came across this question:
A Flat Earth space-time has co-ordinates (t, x, y, z), where z > 0, and a metric
ds2 = ((1 + gz)2)dt2 − dx2 − dy2 − dz2
where g is a positive constant.
Write down the geodesic equations in this space-time...
Hi I'm trying to do a question on nuclear decay chains. The question is:
Bi-210 decays to Po-210 by beta decay (half life = 7.2 days), and this decays by alpha decay to Pb-208 (half life = 200 decays). If A substance is initially pure Bi-210, when does the alpha emmision peak?
So far I've got...
Hi I'm trying to do a question on nuclear decay chains. The question is:
Bi-210 decays to Po-210 by beta decay (half life = 7.2 days), and this decays by alpha decay to Pb-208 (half life = 200 decays). If A substance is initially pure Bi-210, when does the alpha emmision peak?
So far I've got...