Slide1 : Search for extra dimensions at LHC Laurent Vacavant Lawrence Berkeley National Laboratory EPS Aachen / String theory and extra dimensions / 18 July 2003 on behalf of the ATLAS and CMS collaborations
Spectrum of Studies at LHC : Size of extra dimensions Spectrum of Studies at LHC Large Extra Dimensions
direct production of gravitons
virtual effects of gravitons TeV-1-sized ED
Kaluza-Klein excitations of
gauge bosons Warped ED
narrow resonance of graviton
radion TransPlanckian physics:
elastic scattering
black holes (talk by G. Landsberg) Other implications:
gauge coupling unification
singlet neutrino
LHC Studies : LHC Studies Objectives:
establish the sensitivity to the signals
start from Feynman rules derived by theorists
implement the partonic X-sections in a generator
use a fast simulation of detector
acceptance
efficiency
resolution
consider various physics andamp; instrumental backgrounds
try to characterize the model
measurement of unique features
determination of the number of dimensions
parameters of underlying model ?
Detector Performance & Simulation : Detector Performance andamp; Simulation Fast simulation:
many aspects relevant to ED searches validated w/ full sim.:
missing energy (cracks,….): OK for large ET
mass resolution : thorough studies for H Caveat:
systematic effects: linearity at TeV, instrumental bckgd, … Detector Performance:
needed for first searches: missing ET, high-pT electron, photon, …
detectors already optimized for that (SUSY, Higgs)
example: resolution for electrons (ATLAS):
Large Extra Dimensions Kaluza-Klein Gravitons : Large Extra Dimensions Kaluza-Klein Gravitons ADD scenario: (cf. talk by I.Antoniadis)
gravity becomes strong at TeV size of ED 1 mm
SM confined in 4D, only gravity in the bulk
two parameters:
number of extra (compactified) dimensions:
new fundamental mass scale MD: Gravitons andamp; Kaluza-Klein states:
in the bulk: gravitational interaction massless G
in 4D: KK states G(k), mk2 = m02 + k2/RC2
coupling: universal andamp; weak (1/MPl(4)), but large # of states MD~ TeV RC ~ mm (for =2) Constraints (experimental + astrophysics): talk by S.Mele
Large Extra DimensionsDirect Production of Kaluza-Klein Gravitons : Large Extra Dimensions Direct Production of Kaluza-Klein Gravitons Direct production at LHC: Signatures: monojet + missing energy, (photon + missing energy) ATLAS study: partonic cross-sections from
G.Giudice,R.Rattazzi, J.D.Wells
Nucl.Phys. B54 3 (1999)
implemented in ISAJET
ATLAS fast-simulation Background for jet signal:
jZ(), jW(), jW(e), jW() Selection:
trigger: jet (||andlt;5) + ETmiss
lepton veto (||andlt;2.5)
central jet (||andlt;2.5)
large ETmiss ATLAS: LV, I. Hinchliffe J.Phys. G:
Nucl. Part. Phys. 27 1839 (2001)
Large Extra DimensionsDirect Production of Kaluza-Klein Gravitons : Large Extra Dimensions Direct Production of Kaluza-Klein Gravitons Missing energy: Sensitivity for 100 fb-1: jet + G(k) signature: photon + G(k) signature: S/B andgt; 5
andgt; 100 signal events
ET(jet) andgt; 1 TeV 100 fb-1
(1 year @
1034 cm-2s-1) discovery confirm. NB: effective theory, valid only
for MDmin
Large Extra DimensionsDirect Production of Kaluza-Klein Gravitons : Large Extra Dimensions Direct Production of Kaluza-Klein Gravitons Characterization of the model: measure both MD and Precise measurement of Xsection:
difficult:
case (=2, MD= 5 TeV) very similar to
the case (=4, MD= 4 TeV) for instance
not (yet) investigated in details Run at a different CME: s(10 TeV) / s(14 TeV) good discrimination if
5% accuracy on (10)/(14)
andgt; 50 fb-1 @ 10 TeV
new CME close to 14 TeV
(otherwise small overlap of regions
allowed by eff. theory)
Large Extra DimensionsVirtual Exchange of Kaluza-Klein Gravitons : Large Extra Dimensions Virtual Exchange of Kaluza-Klein Gravitons Virtual exchange of gravitons at LHC: Signatures: deviations from SM in Drell-Yan X-sections, asymmetries
(sensitivity mostly from interference terms, KK exchange Ms-8) ATLAS study:
partonic cross-sections
amplitude divergent for andgt; 1:
naive cut-off at Mll, andlt; 0.9 MS
ATLAS: V. Kabachenko, A. Miagkov,
A. Zenin, ATL-PHYS-2001-012 K.Cheung hep-ph/0003306, J.L.Hewett hep-ph/9811356
Large Extra DimensionsVirtual Exchange of Kaluza-Klein Gravitons : Large Extra Dimensions Virtual Exchange of Kaluza-Klein Gravitons Signatures: qq,gg , ll, (WW, tt, …) excess over DY events in di-lepton, di-photon mass distributions
some s-channel processes not present at tree-level in SM:
more central production for
Large Extra DimensionsVirtual Exchange of Kaluza-Klein Gravitons : Large Extra Dimensions Virtual Exchange of Kaluza-Klein Gravitons Sensitivity for 100 fb-1: Mostly a discovery channel:
no sensitivity on
w/o specifying UV theory, Ms cannot be related to MD
TeV-1-sized Extra DimensionsKaluza-Klein Gauge Bosons : TeV-1-sized Extra Dimensions Kaluza-Klein Gauge Bosons Basics: one extra dimension
compactified on a S1/Z2 orbifold
radius of compactification small enough gauge bosons in the bulk
fermions localized on:
a fixed point (M1 model): invariance under y -y
opposite fixed points (M2 model): under y y + 2R
Kaluza-Klein spectra for Z(k), W(k) : mk2 = m02 + k2MC2
for MC = 4 TeV: m1 = 4 TeV, m2 = 8 TeV
look for pp (1)/Z(1) l+l- on top of SM Drell-Yan ATLAS study: matrix elements from T.Rizzo
implemented in Pythia
ATLAS fast simulation T. Rizzo, PRD 61 055005 (2000) ATLAS: G.Azuelos, G.Polesello, Proc. Les Houches 2001 (cf. talk by I.Antoniadis)
TeV-1-sized Extra Dimensions (1)/Z(1) Kaluza-Klein Gauge Bosons : TeV-1-sized Extra Dimensions (1)/Z(1) Kaluza-Klein Gauge Bosons Signatures: (1)/Z(1) e+e-, +- 2 TeV electron in ATLAS: E/E ~ 0.7 % (~20 % for a muon)
acceptance for leptons: || andlt; 2.5
TeV-1-sized Extra Dimensions(1)/Z(1) Kaluza-Klein Gauge Bosons : TeV-1-sized Extra Dimensions (1)/Z(1) Kaluza-Klein Gauge Bosons Sensitivity from peak region: for 100 fb-1, S/B andgt; 5, S andgt; 10 : MCmax = 5.8 TeV Optimal reach (using interferences in tail region): detailed study of systematics:
energy scale, calibration
higher order QCD andamp; EW corrections
PDFs likelihood fit analysis w/ MC experiments
TeV-1-sized Extra Dimensions (1)/Z(1) Kaluza-Klein Gauge Bosons : TeV-1-sized Extra Dimensions (1)/Z(1) Kaluza-Klein Gauge Bosons Characterization of the model: Z(1) or Z ‘ or RS graviton ?? Forward-backward asymetries: 100 pb-1
TeV-1-sized Extra DimensionsW(1) Kaluza-Klein Gauge Bosons : TeV-1-sized Extra Dimensions W(1) Kaluza-Klein Gauge Bosons Ditto for W(1): Sensitivity for 100 fb-1: Discrimination from W ‘: more difficult
under study ATLAS: G.Polesello, M. Prata, preliminary
Warped Extra DimensionRandall-Sundrum model: KK graviton narrow resonance : Warped Extra Dimension Randall-Sundrum model: KK graviton narrow resonance Golden channel: G(1) e+e-
good acceptance
good energy resolution
good angular resolution
also G(1) Main features to check:
universal couplings:
G(1) +-, WW, ZZ, jj
spin 2
measure rc ? KK graviton excitations G(k)
(cf. talk by I.Antoniadis)
scale
coupling andamp; width: c = k/MPl
0.01 andlt; k/MPl andlt; 0.1
mass spectrum:
mn = k xn exp(-krc)
ATLAS: B.C. Allanach, K.Odigari, A. Parker, B. Webber JHEP 9 19 (2000), ditto + M.J.Palmer, A. Sabetfakhri hep-ph/0211205
CMS: C.Collard, M.-C. Lemaire, P.Traczyk, G.Wrochna hep-ex/0207061; I. Golutvin, P.Moissenz, V.Palichik, M.Savina, S.Shmatov Planck brane SM brane
Warped Extra DimensionRandall-Sundrum model: KK graviton narrow resonance : Warped Extra Dimension Randall-Sundrum model: KK graviton narrow resonance Signature: G(1) e+e- ATLAS, e+e-
mG= 1.5 TeV, c = 0.01 CMS, e+e-
mG= 1.5 TeV, c = 0.01 CMS, e+e-
mG= 4 TeV, c = 0.1 100 fb-1 discovery
Warped Extra DimensionRandall-Sundrum model: KK graviton narrow resonance : Warped Extra Dimension Randall-Sundrum model: KK graviton narrow resonance Sensitivity: LHC covers completely the c = k/MPl mG (GeV) CMS, 100 fb-1 interesting region
Warped Extra DimensionRandall-Sundrum model: KK graviton narrow resonance : Warped Extra Dimension Randall-Sundrum model: KK graviton narrow resonance Spin determination: ATLAS, e+e-, 100 fb-1
mG= 1.5 TeV, c = 0.01 Signal:
from gluon fusion
1 – cos4*
from quark annihilation
1 – 3cos2* + 4cos4* Spin-1 (Z ‘): 1 + cos2* Drell-Yan SM NB: acceptance at large
coverage to 2.4-2.5 is
essential
almost no discrimination
spin 1/spin 2 for || andlt; 1.5
Warped Extra DimensionRandall-Sundrum model: KK graviton narrow resonance : Warped Extra Dimension Randall-Sundrum model: KK graviton narrow resonance Spin-1 hypothesis rejection: large fraction of c = k/MPl mG (GeV) CMS, 100 fb-1 interesting region covered by LHC.
Warped Extra DimensionRandall-Sundrum model: the radion : Warped Extra Dimension Randall-Sundrum model: the radion The RS radion:
fluctuations of distance between branes
solving hierarchy problem requires krc~12
dynamical mechanism to do so, gives a mass to the radion, possibly
lighter than G(1) Radion phenomenology:
coupling similar to Higgs, mixes with Higgs ( parameter)
enhanced coupling to gluons
narrow width W.D. Goldberger, M.B. Wise, PRL 83 4922 (1999) G.Giudice, R.Rattazzi, J.D.Wells, hep-ph/0002178 Higgs Radion =0 Radion =1/6 ATLAS: G.Azuelos, D.Cavalli, H.Przysiezniak,LV
Eur.Phys.J direct C4 16 (2002)
Warped Extra DimensionRandall-Sundrum model: the radion : Warped Extra Dimension Randall-Sundrum model: the radion Reinterpretation of Higgs signals: 100 fb-1 SM Higgs
Warped Extra DimensionRandall-Sundrum model: the radion : Warped Extra Dimension Randall-Sundrum model: the radion Decay in two Higgses: hh bb Luminosity (fb-1) required
for 5 discovery: Reach in with 30 fb-1: clean signature
good kinematical constraints
small background max = 2.2 TeV (m=300 GeV) Complementary channel: hh bb max = 1.0 TeV (m=600 GeV)
Higgs doublet & right-handed neutrino : Higgs doublet andamp; right-handed neutrino Model:
gives small masses w/o see-saw
singlet neutrino in the bulk
~ R , coupling reduced by R Study:
charged Higss (2HDM-II)
MSSM: only
in bulk:
asymmetry to discriminate:
measure polarization asymmetries
use hadronic decays ATLAS: K.Assamagan, A.Deandrea,
Phys. Rev D 65 076006 (2002)
Other studies (in a jumble) : Other studies (in a jumble) Large Extra Dimensions:
direct production of graviscalars (stringy effects)
TransPlanckian elastic scattering Universal ED scenario: faking SUSY ?
Disentangling radion and Higgs: coupling measurements Studies not covered in this talk: On-going studies: Next (see Les Houches 2003): Black holes: MC Herwig + simulation (cf. talk by G.Landsberg)
Conclusion : Conclusion A lot of models, with very rich and various phenomenology ! LHC experiments have studied/are studying many of them The LHC will be able to probe the relevant region of the parameter
space for most of the models studied so far Thanks to my colleagues in ATLAS and CMS.
Special thanks to: G. Azuelos, F. Gianotti, L. Pape, L. Poggioli,
G. Polesello, S. Shmatov, P. Traczyk, G. Wrochna