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

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

3 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 SM brane Planck brane Extra Dimension (Bulk) Extra Dimension SM brane Graviton

4 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 This model is slightly warped but large ED ADD model + IR cut-off For n small, this model evades the constrains

5 DELPHI ALEPH OPAL L3 EM CAL : ALEPH DELPHI OPAL

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

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

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

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

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

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

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

13 Conclusion 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. 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 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 In order to select well measured charged particle tracks, 0.4 GeV < p < 100 GeV  p/p ≤ 1.0 measured track length ≥ 30 cm distance to I.P. in r  plane ≤ 4 cm distance to I.P. in z ≤ 4 cm

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