# Presentation: 099899

## Back-to-Back Correlations 

**      **
**Back-to-Back Correlations **
**in p+p, p+A and A+A Reactions**

**2005 Annual AGS-RHIC User's Meeting **
**June 20, BNL, Upton, NY**

**Ivan Vitev**, **LANL**

- June 20, 2005

## Outline of the Talk

**Outline of the Talk**

**Ivan Vitev,** **LANL**

-    **A+A jet triggered correlations: **
**            ********  ****Phase space distribution of non-Abelian energy loss**
**            ********  ****Redistribution of the lost energy in jet triggered correlations**
**            ********  ****Broadening of the away-side correlation function**

-    **p+A reactions at RHIC:**
**            ********  ****Understanding initial and final state multiple scattering**
-               **            **
**            ********  ****Dynamical gluon "shadowing"  -  yields and correlations, **
**                ****including open charm**
**            ********  ****E-loss in cold nuclear matter**

-    **Open charm production and correlations:**
**          ********  ****Partonic subprocesses and cross sections**
-               **            **
**          ********  ****D meson triggered correlations and hadrochemistry  **

- June 20, 2005

## Theoretical Approach

**Theoretical Approach**

- Ivan Vitev, **LANL**

**Collinear factorization approach:   can be systematically expanded to **
**include  nuclear corrections**** **

**Non-perturbative**
**matrix elements: **
**Twist 2, 4, 6, ...**

**Other phenomenologies:  data = model**

**NLO correction at LT**

**Twist: from Opertaor**
**Product Expansion (OPE)**

**Higher twist (elastic) corrections: dynamical shadowing**** **

**Energy loss - enhanced by the nuclear size**** **

**T = Dimension - Spin**

- June 20, 2005

## I. Open Charm Production

**I. Open Charm Production**

- Ivan Vitev, **LANL**

**Popular belief**

**In practice to LO (NLO)**

**Many of the interesting features that follow are related to the **
**                                  ****scattering **

**Time direction**

**from PDFs**

- June 20, 2005

## D0 and D+ at the Tevatron

**D****0**** and D****+**** at the Tevatron**

- Ivan Vitev, **LANL**

**D.Acosta *****et al*****., Phys.Rev.Lett. 91 (2003)**

**Data from:**

** ****Fragmentation functions:  From heavy **
**   ****quark effective field theory (Vector and**
**   ****Pseudoscalar)**

**E.Braaten *****et al*****., Phys.Rev.D 51 (1995)**

**Very reasonable K-factor: K****NLO**** = 1.7**
**Slightly stiffer  power law        **

** ****Branching ratios taken into account**

**...**

- June 20, 2005

## Contribution of PartonicSubprocesses

**Contribution of Partonic****Subprocesses**

- Ivan Vitev, **LANL**

**Define ****partial cross sections**

**Clearly one expects 2 things:**
** ****Dynamical shadowing comparable **
**to light pions  **
** ****Trigger dependent hadrochemistry**

**How to test this? - di-hadron correlations**** **

**Gluon fussion is ****not ****the dominant mechanism for open charm production**

- June 20, 2005

## D Triggered Correlations

**D Triggered Correlations**

- Ivan Vitev, **LANL**

**Never measured before:**

**T.Goldman *****et al*****., in preparation**

**Real possibility for RHIC experiments to **
**discover D meson triggered correlations**
**Constrain D meson production, c quark **
**fragmentation**

** ****Very strong dependence of particle species**
**in the away side jet on p****T2**
** ****Non-monotonic behavior on the away side**
**yields: anti D at  p****T2**** = p****T1**** **

- June 20, 2005

## II. Shadowing in DIS and p+A  

**II. Shadowing in DIS and p+A**

- Ivan Vitev, LANL

**Ivan Vitev,** **LANL**

** ****Decompose **

**Hard part**

**Matrix element**

***Non-perturbative***

***Perturbative***

**Long distance**

**Short distance**

- June 20, 2005

## Numerical Results

- Numerical Results

**J.W.Qiu, I.V., Phys.Rev.Lett. 93 (2004)**

-  Favorable comparison  for the
-   x- and A-dependence NA37 (NMC)
-   and E665 data

**Numerical A- and x****B****-Dependence**

**Ivan Vitev,** **LANL**

**Purely **
**quantum**
**effect**

**The scale of higher twist per nucleon **
**is **_**small**_

- June 20, 2005

## p+A Collisions are not DIS

**p+A Collisions are not DIS**

- Ivan Vitev, **LANL**

** ****p+A collisions do not carry direct information**
**  ****about PDFs (unfortunately all effects)**
** ****Forward (backward) physics not equal**
**  ****small x (large x)**

**1) Initial state energy loss and broadening   -  DY**
**2) Shadowing - DIS**
**3) Final state e-loss is added in p+A **

- June 20, 2005

## p+A Collisions

**p+A Collisions**

- Ivan Vitev, LANL

**Isolate all the**** ****x****b**** ****dependence of the integrand:**

**Resum the ****multiple final state scattering **
**of the parton “d”**** with the remnants of **
**the nucleus**

**p**

**A**

- Starting point: LO pQCD

** ****Other interactions are less coherent (elastic) and  sppressed at**
**   ****forward rapidity by a large scale 1/u, 1/s**

** **- standard parton distribution
-      functions

** **- standard parton distribution
-      functions

**Ivan Vitev,** **LANL**

- June 20, 2005

## Numerical Results

**Numerical Results**

**J.W.Qiu, I.V., hep-ph/0405068**

** **Similar power corrections
-    modification to single and double
-    inclusive hadron production

**- **increases with rapidity and centrality

**Ivan Vitev**, **LANL**

- June 20, 2005

## Forward Correlations

**Statistical errors only**

**25<E********<35GeV**

**35<E********<45GeV**

- Ivan Vitev, LANL

**Forward Correlations**

**Preliminary:**

**L.Bland, [STAR Colaboration]**

** ****There ****is**** room for **
** ****suppression due **
**to power corrections**

** ****There isn’t ****mono **
**jettiness**** **

**Ivan Vitev,** **LANL**

** ****There ****is**** room for **
** ****suppression due **
**to energy loss**

- June 20, 2005

## Dynamical Shadowingto Inclusive D0+D+

**Dynamical Shadowing****to Inclusive D****0****+D****+**

- Ivan Vitev, **LANL**

**Increases with centrality: **
**    ****(dynamical shadowing has little**
**    ****to do with A but with the local**
**    ****path length through nuclear matter)**
**Increases with rapidity:**
**    ****(slightly)**
**Disappears at high p****T****:**
**    ****(power correction type, coherent**
**      ****elastic)**

**Quite similar to light  pions (even slightly larger)**** **

- June 20, 2005

## (D0+D+) - (D0+D-) Triggered Correlations

**(D****0****+D****+****) - (D****0****+D****-****) ****Triggered Correlations**

- Ivan Vitev, **LANL**

**Experimentally probably biased**
**to p****T1**** = p****T2**

**Similar results for the  D meson **
**triggered correlations  **

** ****We know for a fact that  the **
**  ****c quark rescatters (as in DIS) **

** ****In light hadrons **

**Naively expected that the partonic **
**composition will matter but apparently**
**what dominates is: **

**-**

- June 20, 2005

## Energy Loss in Cold Nuclear Matter

**Energy Loss ****in Cold Nuclear Matter**

- Ivan Vitev, **LANL**

** ****Before jumping to conclusions investigate existing data****     **

**  ****Leading twist shadowing: **
**    ****(phenomenology)**** **
**    ****clearly insufficient**** (in fact**
**    ****antishadowing)**

**T.Goldman *****et al*****., in preparation**

**  ****Power corrections  (theory) : **
**    ****clearly insufficient**** (~13%)**

**Leaves additional effects: **
**enegy loss**

**NA35 collaboration: d+Au  (interestingly enough) data  - **

**Same rapidity asymmetry as at **

**h****-**

- June 20, 2005

## One Implementationof Energy Loss

**One Implementation****of Energy Loss**

- Ivan Vitev, **LANL**

**Where energy loss arguably**
**plays a role**

**Bertsch-Gunion bremsstrahlung:**

**Implemented as "Sudakov Form Factors":**

**B. Kopeliovich *****et al*****., hep-ph/0501260 **

**This is one way of implementing energy loss**
**(large rapidity gap events, amplification near**
** ****kinematic bounds)**

- June 20, 2005

## III. Non-Abelian Energy Loss

**III. Non-Abelian Energy Loss**

**Ivan Vitev,** **LANL**

**Naive picture**

**Solution to first order in the mean # of scatterings**

**I.V., hep-ph/0501255**

- +2Re

- June 20, 2005

## Angular and Frequency Behavior 

**Angular and Frequency Behavior**** **

**Ivan Vitev,** **LANL**

**I.V., hep-ph/0501255**

-  Radiation is moderately large angle. Finite gluon number

- June 20, 2005

## Jet Tomography

_**Depletion**_** ****of high-p****T**** hadron multiplicities in Au+Au relative to the binary collision **
**scaled p+p result**** **

**Jet Tomography**

**Ivan Vitev,** **LANL**

**D.d'Enterria, nucl-ex/0504001 (EJP)**

-  **Predicted nuclear **
**   ****modification**
**   ****Non-Abelian energy **
**   ****loss**
**    **
**    ****(GLV formalism) **

**Room for**
**improvement**

- June 20, 2005

## Deriving the Fragmentation Contributions 

**Deriving the Fragmentation Contributions **

**Ivan Vitev,** **LANL**

**Define a measure for nuclear **
**modifications to di-hadron **
**correlations: **

** ****Use ****energy conservation**** to verify the fragmentation sum rule **

**But the formation length is  ~ L/2. **
**May fragment outside the medium**

_**Quenched parent parton**_

_**Feedback gluons**_
**   ****(not DGLAP)**

- June 20, 2005

## Numerical Results

**Numerical Results**

**Ivan Vitev,** **LANL**

**Data is from: **

**J.Adams *****et al*****., **
**nucl-ex/0501016**

**I.V., hep-ph/0501255**

-  **For large energy loss - the ****radiative**** gluons dominate to unexpectedly high **

-  **The redistribution of the energy is a parameter free prediction  **

-  **The amount of energy depends on the trigger p****T****  **

**Very interesting as **
**a function of trigger**

- June 20, 2005

## Superposition of Jet Cones

**Superposition of Jet Cones**

**Ivan Vitev,** **LANL**

**Trigger **
**particle**

_**Some**_** mechanism of **
**jet cone production**

- June 20, 2005

## Independent Verification

**Independent Verification**

**Ivan Vitev,** **LANL**

** ****Practically flat at all angles except **
**   ****very close to the beam pipes**

** ****The distribution of away-side jets comes form**

**How broad is broad?**

**R.Bellwied, RHIC II presentation, April 2005**

** ****It is there in p+p**

** ****Has nothing to do with random walk**

- June 20, 2005

## Projected Medium-Induced Radiation

**Projected ****Medium-Induced Radiation**

**Ivan Vitev,** **LANL**

**From this**

**Additionally: ****acoplanarity**** and ****incomplete jet energy loss****  **

**Approximation**

- June 20, 2005

## Angular Di-Hadron Distribution

**Angular Di-Hadron Distribution**

**Ivan Vitev,** **LANL**

**Because:**

-  **The ****width ****              of the  **
**   ****large-angle correlations**** is **
**   ****dominated  by medium **
**  ****induced gluon radiation**

**I.V., hep-ph/0501255**

** ****Reasessment of the ****origin****  **
**  ****of small and moderate p****T**** **
**  ****away triggered hadrons**

**The quenched parton is not wider**

- June 20, 2005

## Results in Au+Au: STAR

**Results in Au+Au: STAR**

**Ivan Vitev,** **LANL**

**STAR ****preliminary****:**

**Talk by F.Wang, March 2005**

- June 20, 2005

## The Rapidity Story is Known

**The Rapidity Story is Known**

**Ivan Vitev,** **LANL**

- Rapidity coverage

**J.Adams *****et al*****., nucl-ex/0501016, submitted to Phys.Rev.Lett. **

-  Slicing in      and slicing in            is the same

**No (curious) structure**
**in rapidity or azimuth **

- June 20, 2005

## Conclusions

**Conclusions**

-    **Charm triggered correlations are new - p****T**** dependent **
**        ****hadron composition (light hadrons and charm mesons).****  **
**       ****It will be interesting to test experimentally. **
**              **

**Ivan Vitev,** **LANL**

-    **Dynamical power corrections lead to shadowing and **
**        ****suppression of yields and correlations. Has very well **
**        ****defined p****T**** dependence. Additional effects are related to**
**        ****energy loss. Low energy.   **
**            **

-    **Medium induced radiation converts the high p****T**** suppression**
**        ****enhancement  produces large angle  correlations. However **
**        ****there are a number of effects that tend to dilute these **
**        ****signatures.**
**        **
**            **

**  ****If one looks for topological structures one has to do event by **
**       ****event analysis in more detail**

- June 20, 2005