Catalina Petrascu (Curceanu) for the DEAR Collaboration 26th LNF Scientific Committee meeting Frascati, 29 – 30 May 2003

Contents 1.Introduction 2.Kaonic nitrogen: final results 3.Kaonic hydrogen: preliminary results on all the statistics 4.The DEAR scientific program: where we stand 5.Future plans

1. Introduction

Having optimized: - DA  NE for DEAR (luminosity and background); - DEAR: shielding and setup

APD Cryo Cooler Varian Turbo Molecular Pump CryoTiger, CCD Cooling CCD Electronics Vacuum Chamber Hydrogen Target Cell CCD Pre-Amplifier Boards Cooling Lines CCD55-Chip (total of 16 chips)DEAR Cryogenic setup Kaons from DA  NE

DEAR Cryogenic Target Cell

CCD-55 mounting, cryogenics and on-cell electronics - fiber-glass frames - cooling system mounted on the top - minimized Al cold finger (behind CCDs) - reduced diameter of the socket group and, consequently, of the vacuum chamber

DEAR shielding Pb walls Quadrupole shield Pb platform Vacuum jacket shielding Overall shielding factor of the DEAR interaction region ~ 100 Lead shielding Target

November – December 2002 – kaonic hydrogen measurement performed

DEAR on DA  NE autumn 2002

October – December 2002 DAQ Collected data: -Kaonic Nitrogen: 6 – 28 October (about 17 pb -1 – 10 pb -1 in stable conditions); -Kaonic Hydrogen: 30 October – 16 December: about 60 pb -1 -Background data (no collisions) for KH: 16 – 23 December

The first phase of the DEAR Scientific program is completed Results of this phase are hereby presented

2. Kaonic nitrogen: final results

Objectives of kaonic nitrogen measurement # Background study and reduction; optimization of the kaon stopping point distribution (i.e. degrader shaping) # First exotic atom measurement at DA  NE # KN Physics: -yield measurements (exotic atom cascade); - test of a future precision measurement of the charged kaon mass

Kaonic nitrogen: 2002 final results

Kaonic Nitrogen (October 2002) Kaonic Nitrogen (October 2002) integrated luminosity 10 pb -1 (T = 85 K, P = 1.01 bar, density = 4.4 g/l) Pattern of 3 transitions: 7 -> 6 at 4.6 keV 6 -> 5 at 7.6 keV 5 -> 4 at 14.0 keV

Kaonic Nitrogen, 10 pb -1 (October 2002) Background subtracted spectrum Pattern of 3 lines: /- 650 ev. at 4.6 keV /- 395 ev. at 7.6 keV /- 330 ev. at 14.0 keV

First determination of the yield of 3 Kaonic Nitrogen X-ray transitions: 7  6 (33.7 +/ /- 3.4)% 6  5 (55.5 +/ /- 5.5)% 5  4 ( / /- 6.4)% Mass of the kaon – as a test measurement: m K - = / MeV (Ph. D. thesis, paper to be submitted to Phys. Lett. B) Kaonic Nitrogen Physics

3. Kaonic hydrogen (November – December 2002) - preliminary results -

Last Committee (November 2002) presentation:

First Kaonic Hydrogen at DA  NE (Nov. 2002) 20 pb -1 integrated luminosity: 20 pb -1

Kaonic Hydrogen 1800 events in 6.3 keV-region: 500 events Fe 1300 events KH 1800 events in 6.3 keV-region: 500 events Fe events KH JZ / extrapolated

7000 events K  events K-complex Kaonic Hydrogen, 80 pb -1 Monte Carlo simulated spectrum ~ 33eV

Request to the 25th Scientific Committee # To continue until we get an integrated luminosity of at least 80 pb -1 to permit a measurement at the level of ~ 33 eV, assuming the present machine conditions.

What we have obtained: # 60 pb -1 of integrated luminosity which allowed (very preliminary result) a measurement at the level of ~ 40 eV

Two independent analyses were performed: - a global fit of the KH spectrum; - a (measured) background subtracted spectral analysis

I) GLOBAL FIT OF KH spectrum

? Kaonic Hydrogen (2002 data)- global fit 60 pb -1 integrated luminosity: 60 pb KK K complex X-ray energy (KeV) Events/ 60 eV

Kaonic Hydrogen (2002 data)- global fit Background + Fe subtracted spectrum KK K complex X-ray energy (KeV) Events/ 60 eV 124 Ca  Ti  Au - L  Pb Au - L   = (160 +/- 30 +/- 15) eV  = (165 +/- 50 +/- ?) eV KC K  = / ev. K compl = / ?

II) Measured background subtracted spectral analysis

Kaonic Hydrogen (2002 data) Measured Kaonic Hydrogen spectrum KK K complex

Kaonic Hydrogen (2002 data) Measured background spectrum

Kaonic Hydrogen (2002 data) Divided spectrum No Ti No Ca No Fe

Kaonic Hydrogen (2002 data) Normalized measured spectra KK K complex

Kaonic Hydrogen (2002 data) Measured background subtracted spectrum ?  = (165 +/- 40) eV  = (240 +/- 86) eV K  = / ev. K complex = /- 2400

Kaonic Hydrogen (2002 data) Measured background subtracted spectrum - smoothed ?

Results of the KH analyses: Results of the KH analyses: (Very preliminary) Two independent preliminary analyses of the 60 pb -1 collected data were performed – results in very good agreement:  = (162 +/- 40) eV  = ~( 200+/- 80) eV K  = / ev. K complex = /- 2400

4. The DEAR scientific program: where we stand

DEAR and the rest of the world The obtained results: represent the best measurement performed on Kaonic Hydrogen up to now  = (162 +/- 40) eV  = (200+/- 80) eV

Iwasaki et al, 1997 KpX Shift (eV) [  Davies et al, 1979 Izycki et al, 1980 Bird et al, 1983 Constant Scattering Length K-Matrix Potential Model Cloudy Bag Model Consituent Quark Model DEAR preliminary result Kaonic hydrogen: summary of data Width (eV) [  ]

MORE on KH analysis: 1) Refine quality of data – Charge Transfer corrections 2) Finalize the analysis with the good quality data 3) Careful study of the systematic errors 4) Interpretation of the results: challenge for theorist SPRING SCHOOL May - contact with Bern and Bonn groups (Gasser, Rusetsky: Ph. D. Student on KH interpretation – revival of interest)

5. Future plans

Next Steps of the DEAR Scientific Program kaonic hydrogen # few eV precision measurement of kaonic hydrogen 1s level shift; kaonic deuterium # few eV precision measurement of kaonic deuterium 1s level shift in order to determine the isospin dependent antikaon nucleon scattering lengths at percent level precision

Monte Carlo simulations with the SDD triggerable setup (see talk of C. Fiorini) kaonic hydrogen # Percent precision measurement of kaonic hydrogen transition – with 50 pb -1 ;

Kaonic Hydrogen Monte Carlo simulation in realistic conditions Precision on shift ~ 3 eV 50 pb -1 S/B = 1/1

Further plans # Kaonic helium measurement (“kaonic helium puzzle”); # Other light kaonic atoms measurement (Li, Be…); # Charged kaon mass precision measurement # Investigate the possibility of the measurement of other types of hadronic exotic atoms (sigmonium?)

How to reach these goals? NEXT TALK….. (C. Fiorini – Politecnico di Milano )

Acknowledgements The DA  NE machine staff is warmly thanked by the DEAR group. The success of the difficult kaonic hydrogen measurement has its origin in a happy collaboration machine – experiment, which has been continuously enriched by new ideas and clever solutions to all problems.