Difference between revisions of "Pion-pion scattering: the rho resonance"
| Line 14: | Line 14: | ||
===LAB=== | ===LAB=== | ||
| − | * lattice spacing <math>a = 0.0997991 fm</math> | + | * lattice spacing <math>a = 0.0997991 {\rm fm}</math> |
| − | * pion mass <math>m_\pi = 330 MeV</math> | + | * pion mass <math>m_\pi = 330 {\rm MeV}</math> |
* lattice size <math>N_x=N_y=N_z = 18, 20, 22, 24, 26</math> (20 is the lattice size with the smallest difference between the first excited state and the resonance). | * lattice size <math>N_x=N_y=N_z = 18, 20, 22, 24, 26</math> (20 is the lattice size with the smallest difference between the first excited state and the resonance). | ||
* <math>N_t = 48</math> | * <math>N_t = 48</math> | ||
| Line 24: | Line 24: | ||
{| class="wikitable" | {| class="wikitable" | ||
|- | |- | ||
| − | |N || 10 || 12 || 14 || 16 || | + | |N || 10 || 12 || 14 || 16 || '''18''' || '''20''' || '''22''' || '''24''' || '''26''' || 28 |
|- | |- | ||
|L [fm] || 0.997991 || 1.19759 || 1.39719 || 1.59679 || 1.79638 || 1.99598 || 2.19558 || 2.39518 || 2.59478 || 2.79438 | |L [fm] || 0.997991 || 1.19759 || 1.39719 || 1.59679 || 1.79638 || 1.99598 || 2.19558 || 2.39518 || 2.59478 || 2.79438 | ||
| Line 33: | Line 33: | ||
|} | |} | ||
| − | The | + | The bold numbers indicate the relevant sizes to measure <math>\rho</math>. |
Revision as of 00:50, 16 December 2009
\(\pi\pi\rightarrow\rho\) scattering
Craig Pelissier defended his proposal to measure the mass and width of the \(\rho\) resonance. You can find his proposal here.
We will generate two sets of lattices:
- symmetric lattices with cubic symmetry ( _LAB_ )
- elongated lattices ( _COM_ )
Here is the e-mail from Craig regarding the choice of lattice sizes:
LAB
- lattice spacing \(a = 0.0997991 {\rm fm}\)
- pion mass \(m_\pi = 330 {\rm MeV}\)
- lattice size \(N_x=N_y=N_z = 18, 20, 22, 24, 26\) (20 is the lattice size with the smallest difference between the first excited state and the resonance).
- \(N_t = 48\)
Cubic Box in lab frame
| N | 10 | 12 | 14 | 16 | 18 | 20 | 22 | 24 | 26 | 28 |
| L [fm] | 0.997991 | 1.19759 | 1.39719 | 1.59679 | 1.79638 | 1.99598 | 2.19558 | 2.39518 | 2.59478 | 2.79438 |
| E [MeV] | 1032.54 | 966.921 | 917.955 | 880.12 | 850.118 | 825.846 | 805.893 | 789.273 | 775.277 | 763.377 |
| \(m_\pi\times L\) | 1.66905 | 2.00286 | 2.33667 | 2.6704 | 3.0042 | 3.338 | 3.6719 | 4.0057 | 4.3395 | 4.67334 |
The bold numbers indicate the relevant sizes to measure \(\rho\).
- COM**
- lattice spacing $a = 0.0997991 fm$
- pion mass $m_\pi = 330 MeV$
- elongated direction $N_z = 40, 42, 44, 46, 48, 50 ,52, 54, 56$ (48 is the lattice size set such that the first excited state equals the resonance).
- $N_t = 48$
- $N_x=N_y= 24$
- COM Elongated Box $24^2 \times N_z \times N_t$***
$m_\pi \times L_s$ | $L_s$ \[fm\] | $a$\[fm\] | $L_e$\[fm\] | $m_\pi$\[MeV\] | $m_\rho$ \[MeV\]
- -:|:-:|:-:|:-:|:-:|:-:
4.00572 | 2.39518 | 0.0997991 | 4.79036 | 330 | 838.769
E = the energy of the first excited state $p = \frac{2\pi}{L_e}$.
$N_z$ | $40$ | \[42 | 44 | 46 | 48 | 50 | 52 | 54 | 56\] | $58$ -|-|-|-|-|-|-|-|-|-|- $L_e$\[fm\] | 3.99196 | 4.19156 | 4.39116 | 4.59076 | 4.79036 | 4.98996 | 5.18955 | 5.38915 | 5.58875 | 5.78835 E \[MeV\] | 906.325 | 886.314 | 868.598 | 852.841 | 838.769 | 826.152 | 814.799 | 804.55 | 795.266 | 786.834
The brackets indicate the relevant sizes to measure $\rho$.
To generate a lattice spacing with the right value we set $\beta$ using the results quoted in Lattice spacing. We find the following parameters:
- $\beta=5.961$
- $n_{OR} = 8$
- $n_{skip} = 180$
