dhep seminar february 2, 2012

DHEP Seminar February 2, 2012

Gagan MohantyDHEP, TIFR

Personal Recollections from

DHEP Seminar July 29, 2013

Shall roughly follow the sequence given here

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Let’s start with QCD

Inclusive jet and dijet measurements

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Complimentary to inclusive jet measurement m12 is the dijet invariant mass and y is half

the absolute rapidity difference between the two leading jets

Data and theory are in agreement to ~10% with various PDFs

H.D. Yoo

s keeps on running...

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Ratio of the inclusive 3-jet to inclusive 2-jet cross section (R32) with the average pT of the two leading jets (<pT1,2>) ranging between 0.42 and 1.39 TeV

First determination of s from measurements at a Q value above 0.6 TeV Good agreement with the world average value of s(mZ) = 0.11840.0007

®s(mZ) = 0:1148§ 0:0014(exp:) § 0:0018(PDF)+0:0050¡ 0:0000(scale)

Similar results from ATLAS

H.D. Yoo

A text-book plot from CMS

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6 ATLAS has got a similar story to tell

( NLO and NNLO)

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A bit on hadron spectroscopy

Mass (3871.680.17 MeV): Close toD0D*0 threshold Width (< 1.2 MeV, CL=90%): Narrow Production

In pp/pp collisions – rate similar to charmoniaIn B decays – KX similar to cc, K*X smaller than cc

Decay BF: open charm ~ 50%, charmonia ~ few % Nature (very likely exotic)

LooselyD0D*0 bound state (like deuteron)? Mixture of excited c1 andD0D*0 bound state? Many other possibilities: tetraquark etc.?

Find out JPC assignment out of the remaining two possibilities: 1++ and 2+ to pin down its nature

M(+J/) –M(J/) [GeV]

Discovered in 2003

What is the X(3872)?

X(3872)(2S)

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C.Z. Yuan

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JPC=2+ rejected at 8.2!

PRL 110, 222001 (2013)

JPC of the X(3872) is 1++

C.Z. Yuan

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Discovery of a new particle – Zc(3900)

• M = 3899.03.64.9 MeV• = 461020 MeV• 307 48 events• Significance >8

C.Z. Yuan

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What is Zc(3900)? Charged and couples to cc at least four-quark configuration

Clearly exotic – tetraquark, DD molecule, cusp…

PRL 110, 252002 (2013)PRL 110, 252001 (2013)

e+e +J/ at Ecm= 4.26 GeV e+e +J/ from ISR events

• M = 3894.56.64.5 MeV• = 632426 MeV• 159 49 events• Significance >5.2

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Charm, beauty and strange-beauty mesons

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Probing CP violation in charm decays

Is it SM or NP? – a theorist prescription

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RSM is not expected to be greater than 1 for mc >> QCD, but not impossible if we treat the charm-quark to be light

J.F. Kamenik

Check:

Another enigma: semileptonic asymmetry

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Bottom-line:

Current status of the Unitarity triangle

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®=Á2 = ¡88:5+4:7¡ 4:4

¢±

M. Roney

A tantalizing result on B D()

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If the discrepancy with SM holds up, the result cannot be explained by type-II 2HDM; excluded over the full parameter space at 99.8% CL

But can be accommodated in more general extensions of type-III 2HDM

M. Roney

PRL 109, 101802 (2012)

BaBar

Type-II 2HDM

Bs +: almost like a litmus test

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G. Mancinelli

First evidence for Bs +

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Consistent with the SM expectation (3.28109) Set an upper limit on BF(B0 +) < 9.41010 at 95% confidence level

G. Mancinelli

Recently CMS also came with a bang!

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U. Langenegger at EPS2013

arXiv:1307.5025[hep-ex]

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Let’s now go behind the truth!

Why to worry about measuring the top mass?

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The top quark decays well before hadronizing, so one can directly measure its mass by reconstructing various decay products

Indeed, top is the most accurately measured quark (better than 0.5%)

Participates in the quantum loop radiative corrections to the W mass, constraining the Higgs mass (was important till July 2012 discovery)

Now one can use this measurement to assess the self-consistency of SM

The huge mass (almost same as the tungsten atom) puts it close to the scale of EWSB, so the top quark might have a special role in it

So far the most sensitive method at LHC

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A. Castro

LHC average for the top mass

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What about Tevatron?

A. Castro

An unsettled question from Tevatron

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Thanks to pp environment, one can measure the forward-backward asymmetry AFB

J. Varela

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Story so far from the LHC Being a pp machine, LHC does not allow to measure AFB;

we can however measure the charge asymmetry Ac

J. Varela

Another SM candle: W mass

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Current WA is dominated by Tevatron and has a precision of 104B. Quinn

A picture perfect for ILC enthusiasts

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B. Quinn

Probing BSM with charged leptons

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Great prospect ahead to further pin down cLFV with the MEG upgrade, Mu2e, COMET, Project X and Belle II

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Now

Prohibitively small in SM+mass, so constitutes a clean BSM probe

S. Mihara

Neutrino mixing phenomenology

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S. Pascoli

One of the highlighted results on s: sin2(13)

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Y.F. Wang

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Now to the discovery of the decade!

The decay H → γγ: two approaches

Cut-based

Each event category is weighted by its S/(S+B)

only for visualization purposes 32

MVA method is the nominal one while the cut-based approach is there for the cross-check purpose

MVA mass-factorized

A. De Roeck

M(4l)>160 GeV Data 380 evts MC 364.5 evts

(pp ZZ, 8TeV) = 8.41.0 (stat.) 0.7 (syst.) 0.4(lum.) pb

Clean signal peak at ~126 GeV

Good control of the dominant ZZ background

SM(th) = 7.8 0.6 pb

The decay H → ZZ → 4l

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A. De Roeck

The decay H → WW → 2l+2νEvents with 0 jets and different flavour leptons (7+8 TeV Data)

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Exclusion at 95% in the mass range 128-600 GeVLarge excess (4 observed, 5.1 expected at mH 125 GeV) in the low mass region

A. De Roeck

Summary of the five main channels

bb: includes VH and VBFWW: includes ggF, VH, VBF

For a mass of mH = 125.7 GeV CMS-PAS-HIG-13-005

3.4

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Current result

Discovery paper

Expected Observed

3.8 3.2

2.8 4.1

2.4 1.6

1.9 0.7

1.4 0.0

PLB 716, 30-61 (2012)

A. De Roeck

Mass of the new boson

mH = 125.7 ± 0.3(stat) ± 0.3(syst) GeV = 125.7 ± 0.4 GeV

H ZZ4l: mH = 125.8 ± 0.5 (stat.) ±0.2 (syst.) GeVH γγ: mH = 125.4 ± 0.5 (stat.) ±0.6 (syst.) GeV

Signal strengthversus mass

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A. De Roeck

Couplings to fermions and gauge bosons

Overall result

Contributions from all decay channels

Results within 1σ of the SM prediction

For mH = 125.7 GeV(H gg) ~ | kV + kf|

2 / = 0.2, BSM = 0

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A. De Roeck

Discriminant built to describe the kinematics of production and decay of different JP state of a "Higgs"

0+ vs 0-

CLs=0.16%

More JP hypotheses have been tested in a similar way

What about its spin and parity?

Spin/parity hypothesis tests: H → ZZ → 4l channel

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A. De Roeck

Latest news on the Higgs from ATLAS

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7.4 6.6

3.8

1.1

K. Jakobs

ATLAS-CONF-2013-013

ATLAS-CONF-2012-161

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Significances reported in the Discovery paper: 4.5, 3.6 and 2.8 for gg, ZZ and WW

PLB 716, 1-29 (2012)

How does the Higgs couple to SM particles?

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K. Jakobs

Is it a scalar or pseudo-scalar?

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K. Jakobs

How likely it is a tensor (2+) particle?

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K. Jakobs

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Anything else I found interesting?

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C. Galbiati

M. Nicola

P. Zuccon

P. Privetera

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