1,547 reputation
1722
bio website
location
age
visits member for 4 years
seen 14 hours ago

May
13
answered How to determine the direction of medium's displacement vectors of a standing wave?
May
13
comment Caveats when using event-by-event reweightings?
Hmm, I'll write up something or look for a reference when I have time.
May
13
comment Caveats when using event-by-event reweightings?
(Seems you need 50 reputition to comment...) I was asking about the most general case, since this has many uses: Fixing MC, estimating BGs from data, estimating trigger effects without simulating the trigger, .... You give every event a different weight, and make a certain distribution $y$ match perfectly - but have no predictive power there anymode, since data=BG per construction. You hope that in a somewhat correlated distribution $x$ (maybe with a different selection) you now have a better modelling of the BG, but you'll be able to discern the signal, in the simplest case a bump.
May
12
comment Gravity in other dimensions than 3 and stable orbits
I wonder what happens if one just uses a different potental, so that one still has $F \propto 1/r^2$ even in higher dimensions?
May
12
comment Caveats when using event-by-event reweightings?
Say your interested in the dilepton invariant mass, so $y=M_{\ell\ell}$. You believe the angle between leptons is not well modeled, so you correct the $\varphi_{\ell\ell}$ MC distribution ($x$). You would do that in bins of $\varphi$, and you have one factor for each bin. One may determine the factor in a sideband, but applies it to all events. You seem to be thinking about normalizing to the Upsilon peak (~10 GeV), however in the case I mean the total normalization often doesn't change. (By the way, you're answer would better be a comment. We should move this discussion there.)
May
12
asked List of cross sections?
May
12
asked Caveats when using event-by-event reweightings?
May
12
awarded  Informed
Apr
30
comment How to calculate Riemann and Ricci tensors for a sphere?
I'm not sure, can't you just read off the $g_{ij}$, since the differentials are not mixed? For example $g_{\theta\theta} = R^2 \sin^2 \varphi$. I forgot why one is allowed to do that though...
Apr
23
comment Why does Hydrogen molar heat capacity reach 7/2 R?
@Georg: I found it in need of an explanation that the 7th degree of freedom is really a separate DOF. Some simple arguments suggest otherwise: Say #6 is the wiggling, or $\dot p$ of the HO, and #7 is the motion of the center of mass, or $\dot x$. Then a) one variable is determined by the other through the HO DGL, thus they are not independent and b) isn't the movement of the center just a translation?
Apr
23
answered Why does Hydrogen molar heat capacity reach 7/2 R?
Apr
20
comment How to determine predicted CP violation for a given SUSY point?
Thanks. I have some negative mass parameters at the GUT scale (e.g. $M2$), but not negative squared masses, so I don't believe I have complex parameters - at least it was not my intention to introduce them. I was just told in passing by a colleague "Negative mass parameters? That's bad, you'll have too much CP violation!", although he couldn't tell me how exactly, or where he got that.
Apr
4
asked How to determine predicted CP violation for a given SUSY point?
Mar
4
awarded  Enthusiast
Feb
27
comment Local $U(1)$ gauge invariance of QED
@Nivalth: Thanks a lot, but you didn't have to accept it if it didn't help you. Qmechanic and twistor59 also deserve some credit, but unfortunately you don't get points for comments.
Feb
27
answered Local $U(1)$ gauge invariance of QED
Feb
18
asked What dark matter can AMS currently find (or exclude)?
Feb
3
comment What constitutes an observation/measurement in QM?
As far as I understand, decoherence is objective, so no, two observers can't disagree. They can disagree over wheter a system is in a pure or a mixed state. Maybe my use of 'observer' is confusing here. I don't mean something deep like different frames of reference, just that different people (experimentators) have different incomplete knowlege, and that is expressed through their density operators / mixed states. Its like statistical mechanics, but QM.
Jan
30
answered What constitutes an observation/measurement in QM?
Jan
1
comment What is the origin of flavor?
@DavidZaslavsky: Actually, I am asking the same question again. Let me justify it: The first time around, the question was misunderstood by everyone, probably because I wasn't clear enough. I wanted to correct the question, but then the (otherwise fine) answers didn't match anymore, and I was asked to open a new topic with my actual question. I guess the best thing would be to reformulate the other question to match it's answers (I'll be glad if you have any suggestions on how), and to reopen this as my actual intended question.