# Presentation: 137414

## Physics Perspectives for a -Super LHC-

-     Albert De Roeck
- CERN

## LHC Status/plans

- Date for first beams/collisions:               ** Spring 2007**
- Initial physics run starts in summer/fall 2007
-          collect ~10 fb**-1** /exp   (2.10**33**cm**-2** s**-1**)   by early 2008
- Depending on the evolution of the machine...
-          collect  200-300 fb**-1 **/exp (3.4-10.10**33**cm**-2** s**-1**** **) in 5-6 years time

-    Already time to think of upgrading the machine

- Two options presently discussed/studied

- Higher luminosity  ~10**35**cm**-2** s**-1 **** **(SLHC)
- Needs changes in machine and and particularly in the detectors
-   Start change to SLHC mode some time 2013-2016
-  Collect ~3000 fb**-1****/**experiment in 3-4 years data taking.

- Higher energy?
- LHC can reach ****s = 15 TeV with present magnets (9T field)
****s of 28 (25) TeV needs ~17 (15) T magnets  R&D needed!

## Machine

**Upgrade in 3 main Phases**:
-  Phase 0 – maximum performance without hardware changes
-     Only IP1/IP5, N**b** to beam beam limit *L* = 2.310**34** cm**-2** s**-1**
-  Phase 1 – maximum performance while keeping LHC arcs unchanged
-     Luminosity upgrade (*=0.25m,#bunches,...) *L* = 5-1010**34** cm**-2** s**-1**
-  Phase 2 – maximum performance with major hardware changes to the LHC
-     Energy (luminosity) upgrade  E**beam** = 12.5 TeV

- 626

## Machine upgrade

- Latest parameter
- set:
- F. Ruggiero et al.
- PAC2003 report
- May 2003

- (*) Superbunch: 1 bunch of 75 m (rms) in each ring
-      Good for electron cloud effects/bad for experiments: 50000 events/25 ns slice

- A luminosity of
-    10**35**cm**-2** s**-1**
- seems possible

## Detectors: General Considerations

- Normalised to LHC values.

- 104 Gy/year R=25 cm

- In a cone of radius = 0.5 there is ET ~ 80GeV.
- This will make low Et jet triggering and reconstruction difficult.

## Extended Reach: General

- Factor 10 in luminosity extends the
-        reach for Z’ by 1-1.5 TeV.

- -3

- -3

- 0

- 3

- 0

- 3

-  distr. of decay particles

- Z’ = 1 TeV

- Z’ = 5TeV

- Heavy mass: more central

- Mass reach of Z’

- D. Green

- Naïve example: Z’leptons

- Discovery: N > 100

## Luminosity effects

-      HZZ  ee event with M**H**= 300 GeV for different luminosities

- 10**32** cm**-2**s**-1**

- 10**33** cm**-2**s**-1**

- 10**34** cm**-2**s**-1**

- 10**35** cm**-2**s**-1**

## Detectors Upgrades for SLHC

-   hard jets, , large E**T****miss**
-  Major upgrades  (new trackers ..)  for full benefit of higher L:
-    e  ID, b-tag, -tag,  forward jet tagging (?)

- u-jet rejection factor for  (b)=50%

- assuming same 2-track
- resolution at 10**35** as
- at 10**34**

**Detectors Upgrades for SLHC**

** ****Detector Performance**
-  performance at *L *= 10**35** cm**-2**s**-1** is comparable to that at 10**34** cm**-2**s**-1** !!
** ****Integrated Luminosity per Experiment**
-  1000 (3000) fb**-1** per experiment for 1  (3) year(s) of at *L *= 10**35** cm**-2** s**-1**.

- Assumptions for the study

- R&D necessary
- hep-ph/0204087

## Physics Case for the SLHC

- The use/need for for the SLHC will obviously depend on how EWSB
-                  and/or the new physics will manifest itself
- Likely this will only be answered by LHC itself (except if the Tevatron...)
-                 What will the HEP landscape look like in 2012??

-           Rough expectation for the SLHC versus LHC
-  Improvement of SM/Higgs parameter determination
-  Improvement of New Physics parameter determinations, if
-   discovered
-  Extension of the discovery reach in the high mass region
-  Extension of the sensitivity of rare processes

## Extending the Physics Potential of LHC

** ****Electroweak Physics**
-  production of multiple gauge bosons (n**V**  3)
-  triple and quartic gauge boson couplings
-  top quarks/rare decays
** ****Higgs physics**
-  rare decay modes
-  Higgs couplings to fermions and bosons
-  Higgs self-couplings
-  Heavy Higgs bosons of the MSSM
** ****Supersymmetry**
** ****Extra Dimensions**
-  Direct graviton production in ADD models
-  Resonance production in Randall-Sundrum models TeV**-1** scale models
-  Black Hole production
** ****Quark substructure**
** ****Strongly-coupled vector boson system**
-  WLZL g WLZL , ZLZL scalar resonance, W+LW + L
** ****New Gauge Bosons**

- Examples studied
- in some detail

- Include pile up, detector...

- Preliminary...

## Electroweak Physics

-                                     Triple/quartic Gauge couplings
- Production of multiple gauge bosons: statistics limited at LHC
- E.g. # events with full leptonic decays, Pt>20 GeV/c, ||<2.5, 90% eff
- for 6000 fb**-1**

- Use only muon and photon final state channels, statistical errors only
-  Equal or better than LC for  type of couplings, worse for 

- quintuple
- couplings?

- Triple gauge
- couplings:
-    W,WZ
- production

## Electroweak Physics

- Triple gauge couplings: sensitivity

- 14 TeV 100 fb**-1**

- 14 TeV 1000 fb**-1**

- 28 TeV 100 fb**-1**

- 28 TeV 1000 fb**-1**

- Sensitivity into the
- range expected from
- radiative corrections
- in the SM

## Electroweak Physics

- Quartic Gauge Couplings      study pp  qqVV jjVV   (V=W,Z)

- A. S. Belyaev et al:
- Operators leading to
- genuine quartic vertices

- Results for
- events with full leptonic decays,
- P**t**>20 GeV/c, ||<2.5, 90% eff.
- (conservative)

## Top Quark 

-  LHC: M(top)  down to 1.0 GeV  (and M**W**  down to  15 MeV)
- Limited by systematics/no significant improvement expected
- Statistics can still help for rare decays

- tq

- tqg

- tqZ

-   Results in units of 10**-5**
- Ideal = MC 4-vector
- Real  = B-tagging/cuts
-            as for 10**34**cm**-2**s**-1**
- -tag  = assume only B-tag
-            with muons works
-            at 10**35**cm**-2**s**-1**

- Can reach sensitivity down to ~10**-6** BUT vertex b-tag a must at 10**35**cm**-2**s**-1**

## Higgs at SLHC

- Couplings obtained from measured rate in a given production channel:

-  Hadron Colliders: tot and   (pp  H+X)   from  theory  without theory inputs
-   measure ratios of rates in  various channels (tot and  cancel)  f/f’

- Closed symbols: LHC     600 fb-1
- Open symbols:
- SLHC 6000 fb-1

-    SLHC could improve LHC precision by up to ~ 2

**Higgs at SLHC**

- Higgs couplings!

## Rare Higgs Decays

- BR ~ 10**-4** for these channels!
- Cross section ~ few fb

- Additional coupling measurements :
- e.g. **** /**W** to ~ 20%

**Rare Higgs Decays**

- Channels studied:
**   ******** ****H ******** Z******** ******** **********
**   ******** ****H ******** ******

- 3000 fb**-1**

- Note: also a challenge at a LC: e.g. g**H****** ~ 16 % for 1 ab**-1** at 800 GeV

## Higgs Self Coupling Measurements

- Once the Higgs particle is found, try to reconstruct the Higgs potential

- Djouadi
- et al.

- /2 << 3/2

- Difficult/impossible at the LHC

- Too much backgr.

- Dawson
- et al.

## Higgs Self Couplings

**LHC :**  (pp  HH) < 40 fb   mH > 110 GeV
-           +  small BR for clean final states  **no sensitivity**
**SLHC :**  HH  W+ W- W+ W-  ********** ******jj  ************jj   studied

- -- HH production may be  observed for first time at SLHC: ~150 <M**H**<200 GeV
- --  may be measured  with statistical error ~ 20-25%

-  LC : precision up to 20-25% but for M**H **< 150 GeV  (s  500-800 GeV, 1000 fb**-1**)
-         or to ~7-10% for M**H **< 200 GeV (s  3 TeV, 5000 fb**-1**)

- Atlas Study
- Detector Simulation

## Higgs Self Coupling  

- Limits achievable at the 95% CL. for =(-**SM**)/**SM **

- LHC: = 0 can be
- excluded at 95% CL.
- SLHC:  can be determined
- to 20-30%  (95% CL)

- Baur, Plehn, Rainwater

- HH  W+ W- W+ W-  ********** ******jj  ************jj

-   Differences w/t ATLAS study
-  Parton level  Detector Level
-  ATLAS includes parton showers
-  HO cross sections & effects
-  Incorrect simulation ttj in
-   ATLAS study?
-  Jury still out...   CMS starting

## Higgs Self Coupling for low MH

- ppbbbb   not useable
- ppbb    difficult
- ppbb   not useable
- ppbb    promising For m**H**=120 GeV and 600 fb**-1**
-    expect 6 events at the LHC
-    with S/B~ 2  (single b tag)
-  Interesting measurement
-    at the SLHC (double b tag)

- m**vis**

- Needs accurate
- prediction of the
- bb background
- rate
- Needs detector
- simulation

- New

- Baur, Plehn, Rainwater

## Supersymmetry 

-        Impact of the SLHC
- Extending the discovery region
- by roughly 0.5 TeV i.e. from
-        ~2.5 TeV  3 TeV
- This extension involved high
- E**T** jets/leptons and missing E**T**
-  Not compromised by increased
-     pile-up at SLHC

## SUSY Measurements

- Benchmark points  (Battaglia et al./2001)
- Difficult points F,H,K, (M) ...high masses/low event rate
- High Luminosity beneficial to complete further the spectra

- # of particles/species detectable

## Sparticle Mass Measurements

**Proposed Post-LEP Benchmarks for Supersymmetry (hep-ph/0106204)**

- Reconstruction of sbottom (770 GeV) and gluino (920 GeV) for 300 fb**-1**
-                                will need more luminosity!

- After cuts
- ~ 100 events

- Tricomi, Chiorboli

## Example: Point K

- Squarks: 2.0-2.4 TeV        Gluino:    2.5 TeV
- Can discover the squarks at the LHC but cannot really study them

- signal

- Inclusive: M**eff**** **> 4000 GeV
- S/B = 500/100 (3000 fb**-1**)

- Exclusive channel
- qq **1****0 ****1****0 **qq
- S/B =120/30 (3000 fb**-1**)

- Measurements  become possible

- P**t **>700 GeV & E**t****miss**>600 GeV
- P**t** of the hardest jet

- ~~

## MSSM Higgs h,H,A,H

- In the green region only SM-like h observable with 300 fb**-1**/exp
- Red line: extension with 3000 fb**-1**/exp
- Blue line: 95% excl. with 3000 fb**-1**/exp

- Energy dependence

- Heavy Higgs observable region increased by ~100 GeV.

## Other ways to ‘cover the wedge’

- A/H    4 leptons

- Use decays of H,A into SUSY particles, where kin. allowed

- F. Moortgat

- Strongly model/MSSM parameter
- dependent      M2 = 120 GeV,
-                           = -500 GeV,
-                        Msleptons = 2500 GeV,
-                        Msquark, gluino = 1TeV

## Extra Dimension Signals at the LHC

- Graviton production!
- Graviton  escapes detection
- ADD type of ED’s
- Signal: single jet + large missing ET

## Extra Dimensions at (S)LHC

-  Black holes decay immediately (**** ~ 10**-26** s)
- by Hawking radiation (democratic evaporation) :
- large multiplicity, small missing E, jets/leptons  ~ 5

- A  **black hole  event** with  MBH ~ 8 TeV  in ATLAS
- Spectacular signature !

- ...and in CMS

- Large extra dimensions  black holes in the lab?

## Black Holes

- Example:
- Cross sections for
- black holes can be
- very large
- May dominate the
- particle production
- at the LHC
- But can also be
- statistics limited
- for large M**S **and
- M**BH **(add ~ 1 TeV)

- 10 events/
- per year

- Landsberg,Dimopoulos

## Other Extra Dimension Scenarios

-          Randall Sundrum  model
-  Predicts KK graviton resonances
-  k= curvature of the 5-dim. Space
-  m**1 **= mass of the first KK state

- SLHC

- 1001000 fb**-1:** Increase in reach by 25%

-         TeV scale ED’s
-  KK excitations of the ,Z

- Direct: LHC/600 fb**-1       **6  TeV
-            SLHC/6000 fb**-1  **7.7 TeV
- Interf:SLHC/6000 fb**-1  **20 TeV

- T.Rizzo

- 95% excl.
- limits

## Universal Extra Dimensions

- Everybody in the bulk!

- Search: e.g
- 4 leptons +
- E**T****miss**

- e.g. Cheng, Matchev, Schmaltz hep-ph/0205314

- Increase of the sensitivity to R**-1 **from 1.5 TeV to 2 TeV

## Strongly Coupled Vector Boson System

- If no Higgs,  expect  strong VLVL scattering (resonant or  non-resonant) at

**Difficult at LHC. What about SLHC?**
-  degradation of fwd jet tag and central jet veto due to huge pile-up
-  BUT : factor ~ 10 in statistics  5-8**** excess in W+L W+L scattering
- 	 other low-rate channels accessible

**Notes:**
 MZZ = 750 GeV, 4 isolated leptons pT>30 GeV, 2l inv mass compatible with Z
Etag-jet > 400 GeV

##   New Z’ Gauge Bosons

**  ****New Z’ Gauge Bosons**

- Includes pile-up, ECAL saturation...

- Reach:   LHC/600 fb**-1            **5.3 TeV
-              SLHC/6000 fb**-1        **6.5 TeV
-              LHC-28TeV/600 fb**-1   **8 TeV

- with Z-like
- couplings

- S. Godfrey

##  Compositeness

- If  contact interactions
-  excess at low  

-  For this study, no major detector upgrade needed at SLHC
-     (but b-jet tag may be important)

** ****Compositeness**

- 2-jet events:  expect  excess of high-ET  centrally produced  jets.

## Indicative Physics Reach

-           Approximate mass reach machines:
-  s = 14 TeV,   L=1034 (LHC)     :   up to    6.5 TeV
-  s = 14 TeV,   L=1035 (SLHC)   :   up to     8 TeV
-  s = 28 TeV,   L=1034               :   up to    10 TeV

- Units are TeV (except WLWL reach)
- Ldt  correspond to _1 year of running_ at nominal luminosity for _1 experiment_

- † indirect reach
- (from precision measurements)

- PROCESS               LHC           SLHC                           VLHC       VLHC           LC               LC
-                              14 TeV       14 TeV       28 TeV       40 TeV    200 TeV     0.8 TeV     5 TeV
-                              100 fb-1     1000 fb-1    100 fb-1     100 fb-1     100 fb-1      500 fb-1    1000 fb-1
- Squarks                   2.5             3                4                 5             20             0.4             2.5
- WLWL                       2             4             4.5             7           18                             90
- Z’                              5               6               8                11            35                       8†              30†
- Extra-dim (=2)        9              12                     15               25            65                  5-8.5†            30-55†
- q*                            6.5            7.5             9.5               13            75             0.8              5
- compositeness      30             40              40               50           100            100            400
- TGC (****)                0.0014       0.0006        0.0008                       0.0003      0.0004     0.00008

- Ellis, Gianotti, ADR
- hep-ex/0112004+ updates

## Summary

-            The LHC luminosity upgrade to 10**35** cm**-2**s**-1   **(SLHC)
-  Allows to extend the LHC discovery mass/scale range by 25-30%
-  Could allow the first measurement of Higgs self-coupling (20-30%)
-  Allows further access to rear decays such as H, Z, rare top decays...
-  Improved precision on TGCs, Higgs branching ratios,...
- It will be a challenge for the experiments/needs detector R&D starting now
- especially if one wants to be ready to “go” soon after 2013-2014
-    In general: SLHC looks like giving a good physics return for modest cost.
-             Get the maximum out of the (by then) existing machine
-                          An LHC energy upgrade to s ~ 28 TeV
-  Will extend the LHC mass range by factor 1.5
-  Will be easier to exploit experimentally (at 10**34** cm**-2**s**-1)**
-  Is generally more powerful than a luminosity upgrade
-  Needs a new machine, magnet& machine R&D, and will not be cheap

## Expected Detector Performance

** ****Tracking and b-tagging**
-  isolated high pT (> 20 GeV) tracks -  it should be possible to maintain similar efficiency and momentum resolution
-  without a tracker upgrade, for fixed b-tagging efficiency, rejection against light quarks will deteriorate by factor 8-3 (pT ~ 50-200 GeV)
** ****Electron identification and measurement**
-  For electron efficiency of 80% jet rejection decreases by ~ 50%
** ****Muon identification and measurement**
-  If enough shielding is provided expect reconstruction efficiency and momentum resolution not to deteriorate much
** ****Forward jet-tagging and central veto**
-  Essential handle to increase S/N for WW and ZZ fusion processes
-  Performance will be significantly degraded – though algorithms could be optimised
** ****Trigger**
-  high thresholds for inclusive triggers; use of exclusive triggers selecting specific final states, pre-scaling

- The main challenge will be for the detectors

****** **D. Green

## What if Planck Scale in TeV Range?

-   Schwarzschild radius

- Since M**D** is low, tiny black holes
- of M**BH** ~ TeV can be produced if
- partons ij with   ****s**ij** = M**BH**** **pass at a
- distance smaller than R**S**

-  Large partonic cross-section :  **** (ij  BH) ~ **** R**S****2**
**** (pp  BH) is in the range of 1 nb – 1 fb
-         e.g.  For M**D **~1 TeV and n=3, ** **produce 1 event/second at the LHC

-  Black holes decay immediately by Hawking radiation (democratic evaporation) :
-       -- large multiplicity
-       -- small missing E
-       -- jets/leptons  ~ 5

- expected signature (quite spectacular ...)

**What if Planck Scale in TeV Range?**

- R**s**  << 10**-35 **m
- R**s**  ~ 10**-19 **m

- ...within which nothing escapes the gravit. force