Search for one large extra dimension with the DELPHI detector at LEP

1. 2009/5/25 論文会 Search for one large extra dimension with the DELPHI detector at LEP Eur. Phys. J.C (2009) 60:17-23 M1 齋藤智之

2. The hierarchy problem : Gravity is too weak Planck mass Electroweak symmetry breaking scale Too large Hierarchy problem The experimental results including LEP greatly agree with the Standard Model. But, there are some theoretical problems in the SM. The New Physics is needed

3. Extra Dimension (Bulk) SM brane Extra Dimension Graviton Planck brane SM brane Extra dimension • Large (flat) Extra Dimension (ADD) • 4+n dimensions • (n>2, n=1,2 is excluded • by direct gravity tests) • The gravity travels throghout • the extra dimensions • → KK Graviton • Warped Extra Dimension (RS) • 4+1 dimensions • The gravity travels throughout • the extra dimensions • 　　　　　→ KK Graviton

4. ADD model + IR cut-off •This model is slightly warped but large ED •For n small, this model evades the constrains ADD model + The ADD model test was peformed the mode for n≥2 at LEP and Tevatron No excess with SM predictions at the 95% CL

5. ALEPH OPAL DELPHI L3

6. ① 45°<<135° ② 148°<<168° ② 12°<<32° ③ 172°<<176.2° ③ 3.8°<<8° DELPHI detector ② Forward Electro Magnetic Calorimeter ① High-Density Projection Calorimeter ③ Small Angle Tile Calorimeter Radius : 5 m Weight : 3500 t

7. High-density Projection Chamber(HPC) ：measure the three-dimensional charge distribution 90 cm 47 cm Gas Lead 52 cm • •r = 208-260 cm, |z| = 254 cm, • •Granularity : 1degree in phi, 4 mm in z • •Angular resolution : mrad in θ • mrad in  • •Energy resolution :

8. •5 m diameter disk with 9064 lead glass blocks •granlarity : 55 cm ~ 1degree  1 degree • Forward Electro Magnetic Calorimeter (FEMC)

9. Then the events accept the single photon events Data preselection(single photon event) • Why different value? HPC> 0.06 FEMC> 0.10 STIC> 0.30 To remove the mode The cross section decreases with increasing energy and polar angle of photon. •Of more than one photon events • < 2.2°, < 0.8 GeV • within 3°, 15°, 20°from the highest energy photon in the STIC, FEMC, HPC respectively

10. LEP energy : 180 ~ 209 GeV overall luminosity : ~ 650 : the expected distribution from : the data of single photon : the signal expected from for n=1 and =1.25 TeV/c 2 This data are well compatible with expectations from SM processes of selected single photon cosmic ray,  collision, 

11. (n=1) with Results + detector effects (efficiency, energy resolution) In order to agree with this data, The fundamental mass scale at 95 % CL (n=1)

12. (n=1) with Results + detector effects (efficiency, energy resolution) In order to agree with this data, The fundamental mass scale (n=1) at 95 % CL

13. In order to study with n=1 large ED , we have re-analysised single-photon events with DELPHI at LEP at √s=180~209 GeV. Conclusion •The mesuared single photon cross sections are in agreement with the expectations from SM processes •The absence of excesses of events sets of a limit of 1.69 TeV/c at 95 % CL on with n=1 ED

14. Backgrounds

15. • In order to select well measured charged particle tracks, •0.4 GeV < p < 100 GeV •distance to I.P. in r plane ≤ 4 cm •distance to I.P. in z ≤ 4 cm • p/p ≤ 1.0 •measured track length ≥ 30 cm Of the photons, 40%→convert before they reach the HPC 7%→convert in front of the TPC ( →) A useful fraction of these can be reconstructed very precisely. An energy precision : 1.2 % A derectional precision : 1.2 mrad in  and  The conversion radius : 5 mm

16. Energy resolution : 3 % at 45 GeV Spacil resolution : 1.5 degrees in phi , 1 mm in radius Small angle TIle Calorimeter(STIC) 160 tiles Scintillator tiles