Electro-weak Precision Tests with nuSTORM Sanjib Kumar Agarwalla Sanjib.Agarwalla@ific.uv.es IFIC/CSIC, University of Valencia, Spain S. K. Agarwalla, nuSTORM Workshop, Fermilab, USA, 22 nd September, 2012 ¡
Electro-weak Theory The Standard Model (SM) provides a remarkably accurate description of a wide range of phenomena in nuclear and particle physics The SM unifies the weak and electromagnetic forces into one gauge group, SU(2) L × U(1) Y Weak sector è precision at 0.1% level are reached Electromagnetic sector è precision at 1 part per billion The SM is incomplete due to è Ø the discovery of neutrino mass Ø the existence of dark matter Ø the recent advent of dark energy 1/15 S. K. Agarwalla, nuSTORM Workshop, Fermilab, USA, 22 nd September, 2012 ¡
Precision Test Precision low energy observables have been and continue to be an invaluable tool to learn about the scale of new physics and to shed light into flavor sector J. Erler and M.J. Ramsey-Musolf, Prog. Part. Nucl. Phys. 54, 351 (2005) These tests are complimentary to the more canonical measurements done at colliders like LHC looking for new physics at higher energy scales These tests are highly sensitive to the presence of oblique corrections affecting vacuum polarization of the photon, Z and W bosons through new particles in quantum loops and vertex corrections M.E. Peskin and T. Takeuchi, Phys. Rev. Lett. 65, 964 (1990) G. Altarelli and R. Barbieri, Phys. Lett. B 253, 161 (1991) G. Degrassi, A. Sirlin and W.J. Marciano, Phys. Rev. D 39, 287 (1989) 2/15 S. K. Agarwalla, nuSTORM Workshop, Fermilab, USA, 22 nd September, 2012 ¡
Weinberg Angle / Weak Mixing Angle The Weinberg angle is defined by the ratio of the SU(2) L gauge coupling g and the U(1) Y gauge coupling g ′ è a key parameter in the electro-weak theory Its value depends on the energy scale. Renormalization group running of the Weinberg angle is an inevitable consequence of the electro-weak theory Experimental demonstration of the running of the Weinberg angle has been considered to be an experimentum crucis for the SM 3/15 S. K. Agarwalla, nuSTORM Workshop, Fermilab, USA, 22 nd September, 2012 ¡
− ^ Running of sin 2 θ W (MS) 0.25 SM Existing 0.245 Future World data for the Weinberg (MS) SLAC E158 0.24 angle as a function of Q � � dis APV(Cs) W Solid curve shows the � 2 sin 0.235 running in the MS-bar b renormalization scheme A [LEP] Moller [JLab] FB A [SLD] LR 0.23 Qweak [JLab] PV � DIS [JLab] 0.225 0.001 0.01 0.1 1 10 100 1000 Q (GeV) S.K. Agarwalla and P. Huber, JHEP 1108 (2011) 059 4/15 S. K. Agarwalla, nuSTORM Workshop, Fermilab, USA, 22 nd September, 2012 ¡
Discrepancies Leptonic (0.23113 ± 0.00021) and hadronic (0.23222 ± 0.00027) measurements of sin 2 θ W at Z-pole differ by 3.2 standard deviations The ALEPH, DELPHI, L3, OPAL, SLD Collaborations, Phys. Rept. 427, 257 (2006) NuTeV collaboration reported a 3 σ discrepancy with the SM value of sin 2 θ W G.P. Zeller etal., [NuTeV Collaboration], Phys. Rev. Lett. 88, 091802 (2002) [Erratum-ibid. 90, 239902 (2003)] These discrepancies could be a sign for new physics or may be for not understood experimental effects 5/15 S. K. Agarwalla, nuSTORM Workshop, Fermilab, USA, 22 nd September, 2012 ¡
sin 2 θ W .vs. Higgs mass 0,l A 0.23099 ± 0.00053 fb A l (P � ) 0.23159 ± 0.00041 A l (SLD) 0.23098 ± 0.00026 0,b A 0.23221 ± 0.00029 fb ¤ SM prediction for sin 2 θ W as 0,c A 0.23220 ± 0.00081 fb a function of Higgs mass had Q 0.2324 ± 0.0012 fb Average 0.23153 ± 0.00016 ¤ Precise information on � 2 /d.o.f.: 11.8 / 5 10 3 sin 2 θ W is very helpful to m H [ GeV ] constrain the Higgs mass 10 2 �� (5) �� had = 0.02758 ± 0.00035 m t = 178.0 ± 4.3 GeV 0.23 0.232 0.234 lept sin 2 � eff 6/15 S. K. Agarwalla, nuSTORM Workshop, Fermilab, USA, 22 nd September, 2012 ¡
nuSTORM Near Detector Setup D e t e c t o r d e p t h = 22 . 5 7 m L = 2 0 m / 5 0 m / 1 00 m S tr a i g h t se c t i o n = 1 5 0 m R a di u s = 2 . 8 m � d x x 25 m A r c d l l 1 k t L A r d e t e c t o r S t o r a g e R i n g ¤ E µ = 3.8 GeV with 1.8 × 10 18 effective µ + decays in 5 years ¤ Length of the Straight Section = 150 m ¤ Distance between the front end of the storage ring and detector = 20 m / 50 m / 100 m ¤ 1 kt LArTPC (Radius = 2.8 m & Length = 22.57 m) with 100% efficiency ¤ Energy resolution, σ (E) in GeV = 5% × √ E in GeV ¤ 50 MeV bin-size in reconstructed recoil kinetic energy 7/15 S. K. Agarwalla, nuSTORM Workshop, Fermilab, USA, 22 nd September, 2012 ¡
Geometry Integrated Flux 20 m, 1 kt 50 m, 1 kt 100 m, 1 kt 50 m, 60 tons 100 m, 60 tons 20 m, 60 tons Work in progress with Christopher Tunnell 8/15 S. K. Agarwalla, nuSTORM Workshop, Fermilab, USA, 22 nd September, 2012 ¡
ν -e scattering Simple, purely leptonic, weak interactions, plays an essential role to prove the validity and perform precision tests of the SM E ν = Incoming neutrino energy , T = Electron recoil kinetic energy θ = Angle between incident neutrino direction and recoil electron The values of α and β in the SM for different processes The signal is a forward electron track with no hadronic activity The transverse momentum of the outgoing electron is very small, 9/15 S. K. Agarwalla, nuSTORM Workshop, Fermilab, USA, 22 nd September, 2012 ¡
CCQE .vs. ν -e scattering Main source of background in 1000 studying the ν -e scattering process CCQE is quasi-elastic ν e N scattering 100 But, the transverse momentum of [10 m ] 2 the outgoing electron is very large 10 � 45 for CCQE process compared to ν -e scattering 1 electron neutrino � e scattering � CCQE : 0.1 ν -e scattering : 0.01 We can use the p t and E e cut to 0.5 1 1.5 2 2.5 3 3.5 4 reject most of the CCQE E [GeV] � backgrounds provided that the detector has very good angular and energy resolution! Work in progress with Christopher Tunnell 10/15 S. K. Agarwalla, nuSTORM Workshop, Fermilab, USA, 22 nd September, 2012 ¡
CCQE Background Study Looking for electron neutrino Deep-inelastic backgrounds rejected looking at the hadronic activity Further cuts like: E p > 50 MeV and θ p > 20 degrees Work in progress with Christopher Tunnell 11/15 S. K. Agarwalla, nuSTORM Workshop, Fermilab, USA, 22 nd September, 2012 ¡
Queries on LArTPC ¤ What type of electron energy resolution can we expect? ¤ What type of angular resolution can we expect for LAr? ¤ HIRESMNU has 0.2 degrees for 2 GeV electrons ¤ Intrinsic angular resolution limited to 1 degree from accelerator Work in progress with Christopher Tunnell 12/15 S. K. Agarwalla, nuSTORM Workshop, Fermilab, USA, 22 nd September, 2012 ¡
Signal with and without cut 600 600 w/o cut w/ cut 500 20 m, 1 kt 500 20 m, 1 kt Muon energy = 3.8 GeV Events per 50 MeV Bin Events per 50 MeV Bin Distribution of signal events 50 m, 1 kt 400 400 nue & numubar convoluted 50 m, 1 kt 300 300 100 m, 1 kt 200 200 100 m, 1 kt 100 100 0 0 0.5 1 1.5 2 2.5 3 3.5 4 0.2 0.4 0.6 0.8 1 1.2 1.4 Reconstructed Electron energy [GeV] Reconstructed Electron energy [GeV] Work in progress with Christopher Tunnell To reject CCQE background, we consider an energy window of 0.05 GeV to 1.5 GeV in reconstructed recoil electron kinetic energy and an angular cut of cos θ > 0.9961946 13/15 S. K. Agarwalla, nuSTORM Workshop, Fermilab, USA, 22 nd September, 2012 ¡
Event Rates and Precision Total neutrino electron scattering event rates in 1 kt detector We consider an energy window of 0.05 GeV to 1.5 GeV in reconstructed recoil electron kinetic energy and an angular cut of cos θ > 0.9961946 Relative error on weak mixing angle at 1 σ Work in progress with Christopher Tunnell 14/15 S. K. Agarwalla, nuSTORM Workshop, Fermilab, USA, 22 nd September, 2012 ¡
nuSTORM 0.25 SM Existing Preliminary nuSTORM will provide Future 0.245 a ≈ 1.5% measurement of weak mixing angle at Q ≈ 2 GeV (MS) SLAC E158 0.24 � � dis More studies on APV(Cs) W � electro-weak 2 sin nuSTORM 0.235 measurements will b A [LEP] come soon! Moller [JLab] FB A [SLD] LR 0.23 Qweak [JLab] Thank you! PV � DIS [JLab] 0.225 0.001 0.01 0.1 1 10 100 1000 Q (GeV) Work in progress with Christopher Tunnell 15/15 S. K. Agarwalla, nuSTORM Workshop, Fermilab, USA, 22 nd September, 2012 ¡
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