Attempt to solve alignment problem with E/p ratio

(very preliminary)

04.11.2003 Weekly meeting

Motivation (1)

An alternative way to find time dependent term for momentum correction (misalignment variation in time)

using LKr.

For e+ and e- we compare E (measured by LKr) with

P (measured by spectrometer).

Motivation (2) Momentum distortions:

Preal = Pobservable + PM + PAC + PAT (t)where:

PM – magnetic field correction

PAC – constant misalignment correction

PAT (t) – time dependent misalignment correction Energy measured by LKr:

Ereal = Eobservable + E ,where the corrections E is expected to be time independent. The correction PAT will be connected with E/p ratio:

PAT(t) + Pconst= E – P = P (E/P – 1).

Selection (1) We need “pure” electrons and positrons coming from:

K 0D

Selection: 3 tracks coming from 1 vertex Only 1 vertex Time window 40 ns Track time < 10 ns 1 unassociated cluster in LKr with E>2 GeV Zvertex < 8500 cm RCOG < 2 cm No E/p conditions for e+, e- and .

In case of three tracks we have two possible mass solutions for a given charge of the kaon (we know what exactly is the “odd” particle and the “even” particles can swap their masses). We take the combination, which mass is more close to the PDG value of the kaon mass.

To exclude additional background, we remove events with mee<0,01 GeV.

Selection (2)

E/p spectraMass spectra

|M-MPDG|<0,01

E/p for supersample I

Without PM correction… With PM correction (B corrected to put <M+3 + M-3>/2=MPDG)

e+(K+) e-(K+)

e-(K-)e+(K-)

e+(K+) e-(K+)

e-(K-)e+(K-)

E-p for supersample I

Without PM correction… With PM correction.

e+(K+) e-(K+)

e-(K-)e+(K-)

e+(K+) e-(K+)

e-(K-)e+(K-)

E/p and E-p for supersample II

E/p E-p

e+(K+) e-(K+)

e-(K-)e+(K-)

e+(K+) e-(K+)

e-(K-)e+(K-)

To do…

Check the correction on B field. Corrections dependencies of (X,Y)DCH, P

e.t.c. Apply the obtained corrections to pions

from K3 and check the mass split. Check another source of electrons and

positrons.