Phenomenology of bulk scalar production at the LHC A PhD oral examination A PhD oral examination By Pierre-Hugues Beauchemin

A Small Title Analysis Phenomenology: Phenomenology: Study of the essential structure of nature that relates empirical observations of phenomena to each other in a way which is consistent with a fundamental theory, but without being directly derived from it. Study of the essential structure of nature that relates empirical observations of phenomena to each other in a way which is consistent with a fundamental theory, but without being directly derived from it. The structures (ingredients) of our theoretical framework is motivated by the more fundamental String Theory Jargon: Conceptual framework designed to relate Dark Energy measurement to possible High Energy physics observations From this, physical predictions can be made for a specific experimental context My work stand on the bridge between theory and observation

What kind of predictions are under concern here? Scalar production: Scalar production: Controlled production or “creation” of a specific type of particle that haven’t been observed yet but is predicted by our theoretical framework. Controlled production or “creation” of a specific type of particle that haven’t been observed yet but is predicted by our theoretical framework. Jargon This scalar is gravitational interacting spinless particle The physical predictions consist in deriving the Feynman rules of their coupling to ordinary field and to compute their cross section, ie their rate of production for a specific experiment Part of my work consisted in using the theoretical framework to compute these quantities for scalar direct production processes

At the LHC At the LHC The LHC is the experimental setup which will provides the empirical observations that could reveal the phenomena under study. The LHC is the experimental setup which will provides the empirical observations that could reveal the phenomena under study. Jargon The LHC is a Proton- Proton collider at 14 TeV so it can probe high mass and high P T states. The LHC and Atlas detector design are optimized for new physics search To “see” the collision products, 4 detectors will be build on the 27 km LHC ring. The second part of my work consist in determine if the physics predictions that I computed from our theoretical framework can experimentally be tested with the ATLAS detector at the LHC

However… There are already existing studies of the “phenomenology of scalar production at the LHC”. There are already existing studies of the “phenomenology of scalar production at the LHC”. e.g.: Higgs search So what is new, different and interesting about what I studied??? ANSWER : BULK Completely new theoretical framework, phenomena, set of predictions and experimental signatures Extra dimensions

Does it make sense to consider that the world is 4+n dimensional? Does it make sense to consider that the world is 4+n dimensional? OF COURSE! There are examples of everyday life of objects with more dimensions than we see.

What do we need to assert that the fundamental structure of the Universe have such a extra dimensions? Some theoretically motivated concept or mechanism that account for the fact that so far precise particle physics experiment haven’t seen such extra dimensions. Some theoretically motivated concept or mechanism that account for the fact that so far precise particle physics experiment haven’t seen such extra dimensions. A way to justify that we can probe them. A way to justify that we can probe them. The solution come from String Theory!

String Theory predicts the existence of branes Our world as a 3-brane on which every SM fields are confined. Gravity is not confined to such brane.

Moreover… If we add supersymmetry to our framework, we will have the ingredients to solve probably the most annoying problems of fundamental physics: If we add supersymmetry to our framework, we will have the ingredients to solve probably the most annoying problems of fundamental physics: The cosmological constant problem Recall the problem: Recall the problem: The vacuum energy predicted by quantum field theory is much bigger (10E60 times) than our Dark Energy measurement in the c.m.b. anisotropy (WMAP) This new, well-motivated, rich and explanatory theoretical framework will be called the SUPERSYMMETRIC LARGE EXTRA DIMENSIONS (SLED) scenario

What is SLED involves ? In order to be able to solve the cosmological constant problem, SLED requires: In order to be able to solve the cosmological constant problem, SLED requires: Exactly 2 extra dimensions of O (10  m) Exactly 2 extra dimensions of O (10  m) SM particles stuck to a 3-brane SM particles stuck to a 3-brane N=2 SUperGRAvity in the bulk N=2 SUperGRAvity in the bulk SUSY strongly broken on the brane SUSY strongly broken on the brane Bulk SUSY breaking scale of O (10 -3 eV) Bulk SUSY breaking scale of O (10 -3 eV) We can use these structures to write down a low-energy 4D effective quantum field theory that generically couple the KK-states of a massless bulk scalar to the brane SM fields and draw physical predictions from it!

MY WORK THUS CONSIST IN: MAKING THESE PREDICTIONSMAKING THESE PREDICTIONSMAKING THESE PREDICTIONSMAKING THESE PREDICTIONS and USE THEM TO SHOW HOW SUCH THEORY IS TESTABLE AT THE LHC

Plan of the analysis Write the effective 4D low-energy Lagrangian describing the coupling of a SLED bulk scalar to SM field Write the effective 4D low-energy Lagrangian describing the coupling of a SLED bulk scalar to SM field Concentrate on the lowest mass dimension interaction term to: Concentrate on the lowest mass dimension interaction term to: Quarks and gluons Quarks and gluons Higgs bosons Higgs bosons Evaluate the possibility to observe such scalar with the ATLAS detector by studying: Evaluate the possibility to observe such scalar with the ATLAS detector by studying: Jet+ T miss :Beauchemin et al. (J. Phys. G: Nucl. Part. Phys. 31) Jet+E T miss :Beauchemin et al. (J. Phys. G: Nucl. Part. Phys. 31) H+E T miss :Beauchemin et al. (J. Phys. G: Nucl. Part. Phys. 30) H+E T miss :Beauchemin et al. (J. Phys. G: Nucl. Part. Phys. 30)

LAGRANGIAN This formal object summarize all the structures contained in SLED and describe the dominant coupling of a bulk scalar  with the SM fields. Coupling to quarks and gluons: Coupling to Higgs bosons:

Cross sections From this we can predict the distributions for all the experimental observables: P T, , E T miss, etc. Extra dimensions phase space factor: Jet+E T miss

Where we followed the conventions of [hep-ph/ ]: After having compute these differential cross section, I wrote Monte Carlo programs using PYTHIA to perform the integrations numerically and to generate the events used to simulate ATLAS detector’s outcomes.  +E T miss

Jet+E T miss Experimental Analysis The main standard background (ie. known events that leave the same jet+E T miss signature in the detector) are The main standard background (ie. known events that leave the same jet+E T miss signature in the detector) are  pp→jet+Z(→ ) (277.6 fb)  pp→jet+W(→e e ) (364.2fb)  pp→jet+W(→   ) (363.7 fb)  pp→jet+W(→   ) (363.3 fb) P T jet ≥ 500 GeVProc.:Jet+… Z → Z → W → e W → e W→W→W→W→ W→nW→nW→nW→n Bulk scalar Total No lepton  j1-  j2 ≤2.83  j1-  j2 | ≤

Results Discovery criteria: % certainty that it is not a statistical fluctuation With the background events (PT≥500 GeV), it is required that: S ≥ 970 events  σ(pp→jet+φ) ≥ 10.9 fb where

To be valid and testable at the LHC, any model of bulk scalar must satisfy the following inequalities that show the ATLAS sensitivity to this new physics:

 +E T miss Experimental Analysis The main standard background are: The main standard background are:  qq→  (56.2 pb)  gg→  (49.0 pb)  QCD jet-jet ( 7.0 pb)  QCD  -jet(15.0 pb)  qq→hZ→  (1.22E-3 pb)  qq→tth (h→  )(1.28E-3 pb) After applying standard cuts for h→  search: SPECIFIC TO SLED

But looking to these graphs, we can see that we can get a Better sensitivity of we also apply a cut on E T miss

Conclusion SLED scenario offers a fundamentally new understanding of high energy physics and thus deserves to be carefully studied SLED scenario offers a fundamentally new understanding of high energy physics and thus deserves to be carefully studied SLED has a rich phenomenology. In particular, it predicts coupling of bulk scalars to SM particles. SLED has a rich phenomenology. In particular, it predicts coupling of bulk scalars to SM particles. I computed physical predictions for fairly generic bulk- scalar and bulk scalar-Higgs interactions I computed physical predictions for fairly generic bulk- scalar and bulk scalar-Higgs interactions I then showed that this theory can be tested at the LHC I then showed that this theory can be tested at the LHC Using cut on ETmiss, I evaluate ATLAS sensitivity to: Using cut on ETmiss, I evaluate ATLAS sensitivity to: qq  : 0.26 ≲ g ≲ 1 qq  : 0.26 ≲ g ≲ 1 gg  : 0.06 ≲ c ≲ 1 gg  : 0.06 ≲ c ≲ 1 hh  : 0.09 ≲ a ≲ 1 hh  : 0.09 ≲ a ≲ 1

Back-up slides

What do gain from these considerations? This brane technology allows for extra dimensions as big as O (10  m) across. This brane technology allows for extra dimensions as big as O (10  m) across. Explain why gravity is so weak. Explain why gravity is so weak. Experimental test of the Newton law (classical) at distance scales smaller than the radius R of the extra dimensions. The D-dimensional Planck scale will be: We can study quantum gravity in colliders!

Feynman rules qq  : gg  : ggg  :