Difference between revisions of "Pion-pion scattering: the rho resonance"
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Revision as of 11:34, 17 December 2009
Contents
\(\pi\pi\rightarrow\rho\) 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 \(a = 0.0997991 {\rm fm}\)
- pion mass \(m_\pi = 330 {\rm MeV}\)
- 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 bold numbers 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:
- \(\beta=5.961\)
- \(n_{OR} = 8\)
- \(n_{skip} = 180\)
